Book Name | : | Target Book |
Paper Type | : | School Test Question Paper (2024 – 2025) |
Paper Category | : | Madhyamik Suggestion |
School | : | Tamluk Hamilton High School |
Question – 1
Choose the correct answer for each of the following questions: [1 × 6 = 6]
(i) If the ratio of a principal and its amount in 1 year is 25 : 28, the rate of interest per annum is:
(a) 3 %
(b) 12 %
(c) 10 5\over7 %
(d) 8 %
Answer
(b) 12 %
Explanation:
Amount (A) = 28x
Principal (P) = 25x
Time (T) = 1 year
or, 28 = 25 × (1 + R \over 100)
or, 28 \over 25 = (1 + R \over 100)
or, 28 \over 25 – 1 = R \over 100
or, 3 \over 25 = R \over 100
or, R = 3 \over 25 × 100 = 12 %
(ii) The condition of being two roots of the equation ax² + bx + c = 0 are opposite in sign is:
(a) b = 0
(b) b < 0
(c) c/a < 0
(d) c/a > 0
Answer
(c) c/a < 0
(iii) The lengths of radii of two circles 3 cm and 4 cm and distance between two centres is 10 cm, numbers of common tangents of two circles are:
(a) 0
(b) 2
(c) 3
(d) 4
Answer
(d) 4
(iv) If sin A + sin B + sin C = 3, where 0 ≤ A, B, C ≤ 90°, then the value of sin A + B + C\over 6 is:
(a) 0
(b) 1\over 2
(c) 1\over √2
(d) 1
Answer
(c) 1\over √2
Explanation:
sin A + sin B + sin C = 3
sin A = 1 | sin B = 1 | sin C = 1 |
or, sin A = sin 90º
or, A = 90º |
or, sin B = sin 90º
or, B = 90º |
or, sin C = sin 90º
or, C = 90º |
sin A + B + C\over 6 = sin 90º + 90º + 90º\over 6
= sin 270º\over 6
= sin 45º = 1\over √2
(v) Determine the ratio of the volumes of a solid right circular cylinder, a solid right circular cone, and a solid sphere of equal diameter and equal height:
(a) 3 : 2 : 1
(b) 3 : 1 : 2
(c) 2 : 3 : 1
(d) 1 : 2 : 3
Answer
(b) 3 : 1 : 2
Explanation:
Vcylinder = πr²h = 2πr³
Vcone = 1\over3πr²h = 2\over3πr³
Vsphere = 4\over3πr³
Vcylinder : Vcone : Vsphere = 2πr³ : 2\over3πr³ : 4\over3πr³
= 2 : 2\over3 : 4\over3
= 1 : 1\over3 : 2\over3
= 3 : 1 : 2
The ratio of the volumes is 3 : 1 : 2.
(vi) The median of the data 2, 8, 2, 3, 8, 5, 9, 5, 6 is:
(a) 8
(b) 6.5
(c) 5.5
(d) 5
Answer
(d) 5
Explanation:
The given data is: 2, 8, 2, 3, 8, 5, 9, 5, 6.
Arranging in ascending order: 2, 2, 3, 5, 5, 6, 8, 8, 9.
Median position = \text{n + 1}\over2 = \text{9 + 1}\over2 = 5
The 5th value in the ordered data is 5.
Question – 2
Fill in the blanks (Any Five):
(i) Two types of partnership business are ______ and ______.
(ii) If x is proportional to 1/y and y is proportional to 1/z, then x is proportional to ______.
(iii) Cyclic parallelogram is a ______ figure.
(iv) The value of cos 9° cos 18° cos 36° cos 72° cos 90° cos 144° is ______.
(v) If the numerical values of volume and lateral surface area of a right circular cylinder are equal, then the length of the diameter of the cylinder is ______ unit.
(vi) From two types of Ogives, the value of ______ is determined.
Answer
(i) General partnership and limited partnership
(ii) z
(iii) Rectangle
(iv) 0
(v) 4 units
(vi) Median
Question – 3
State whether True or False (Any Five):
(i) Conjugate surd of √5 + √3 is √5 – √3.
(ii) A started a business with ₹10,000; after 6 months, B joined the business with ₹20,000. At the end of the year, the profit share of each of them will be equal.
(iii) If 0° < θ < 90°, then sin²θ = sin²20°.
(iv) Right circular cylinder has three surfaces.
(v) If the median of arranging the ascending order of data 8, 9, 12, 17, x+2, x+4, 30, 31, 34, 39 is 15, then the value of x is 21.
(vi) If lengths of two corresponding medians of two similar triangles are 5 cm and 7 cm respectively, then the ratio of the areas of triangles is 25 : 49.
Answer
(i) True
(ii) False
(iii) False
(iv) True
(v) True
(vi) True
Question – 4
Answer the following Questions (Any Ten):
(i) The rate of simple interest per annum reduces to 3 ¾ % from 4% and for this, a person’s annual income decreases by ₹ 60. Determine the principal.
Answer
Principal = P
Rate (r) = 4 % – 3 ¾ = 1\over 4 %
Interest (I) = ₹ 60
Time (t) = 1 year
P = \text{I} × 100\over \text{r × t} = 60 × 100\over {1\over 4} × 1 = ₹ 24,000
(ii) In a partnership business, the ratio of capitals of A, B, and C is 1\over6 : 1\over5 : 1\over4. If at the end of the year the profit of the business is ₹3700, find the profit share of C.
Answer
Ratio of capitals of A, B, and C = 1\over6 : 1\over5 : 1\over4
To simplify, take the LCM of the denominators (6, 5, and 4), which is 60. Multiply each term in the ratio by 60
= 1\over6 × 60 : 1\over5 × 60 : 1\over4 × 60
= 10 : 12 : 15
Sum of Ratio = 10 + 12 + 15 = 37
The profit of the business is ₹3700.
Profit of C = ₹ 15\over37 × 3700 = ₹ 1500
The profit share of C is ₹1500.
(iii) For what value of k, the sum of the square of the roots of the equation 6x² + x + k = 0 is 25\over26.
Answer
Sum of the roots (α + β) = –1\over6
Product of roots (αβ) = k\over6
Now, α² + β² = (α + β)² – 2αβ
= (-1\over6)² – 2 × k\over6
= 1\over36 – k\over3
or, 25\over26 = 1 - 12k\over36
or, 1 – 12k = 25\over26 × 36
or, 12 k = 1 – 900\over26
or, k = 26 - 900\over26 × 12
or, k = – 874\over312 = – 437\over156
(iv) Find out the simplest value of \sqrt{4+ \sqrt{15} } -{1\over2}\sqrt{10}
Answer
Given: \sqrt{4+ \sqrt{15} } -{1\over2}\sqrt{10}
= \sqrt{4 \times 4+ 4 \times\sqrt{15} \over4} – {1\over2}\sqrt{10}
= {1\over2}\sqrt{16+ 4\sqrt{15}} – {1\over2}\sqrt{10}
= {1\over2}\sqrt{(\sqrt{10})^2 + (\sqrt{6})^2+ 2\sqrt{10}\sqrt{6}} – {1\over2}\sqrt{10}
= {1\over2} \sqrt{(\sqrt{10} + \sqrt{6})^2} – {1\over2}\sqrt{10}
= {1\over 2} (\sqrt{10} + \sqrt{6}) – {1\over2}\sqrt{10}
= {\sqrt{10}\over2} + {\sqrt{6}\over2} – {1\over2}\sqrt{10}
= {\sqrt{6}\over2}
(v) In the adjoining figure, O is the center of the circle, OP ⊥ AB; AB = 6 cm, and PC = 2 cm. Determine the radius of the circle.
Answer
PC = 2 cm
OP = r – 2
OB = r
PB = 1\over2AB cm = 3 cm
Applying pythagoras theorem:
OB² = PB² + OP²
or, r² = 3² + (r – 2)²
or, r² = 3² + r² – 4r + 4
or, 4r = 13
or, r = 3.25 cm
(vi) In Δ ABC, ∠ABC = 90°, and BD ⊥ AC. If BD = 8 cm and AD = 4 cm, then determine the length of CD.
Answer
In the right-angled triangle ABC, with ∠ABC = 90°, the altitude BD is drawn from the right angle B to the hypotenuse AC.
This divides AC into two segments AD and DC.
BD² = AD × DC
Given: BD = 8 cm and AD = 4 cm.
Substitute these values into the relation: (8)² = 4 × DC
64 = 4 × DC
DC = 64 ÷ 4
DC = 16 cm
Thus, the length of CD is 16 cm.
(vii) In the adjoining figure, O is the center of the circle, AB is the diameter, ∠AOD = 140°, and ∠CAB = 50°, then find ∠BED.
Answer
Given that ∠AOD = 140°
∴ reflex ∠AOD = 360° – 140° = 220°
Again, the central angle produced by the arc ÂBD is reflex ∠AOD and angle in circle = ∠ACD
∴ reflex ∠AOD = 2∠ACD
or, 220° = 2∠ACD
∴ ∠ACD = 220°\over2 = 110°
Given that ∠CAB = 50°
Now, in ΔACE,
∠AEC + ∠EAC + ∠ACE = 180°
or, ∠AEC = 180° – 50° – 110° = 20°
Hence ∠BED = 20°
(viii) In Δ ABC, a parallel line to BC intersects the sides AB and AC at P and Q respectively. PB = AQ, AP = 9 units, QC = 4 units. Find the length of PB.
Answer
Let PB = x. Given that PB = AQ, we also have AQ = x.
From the given data:
- AP = 9 units
- QC = 4 units
Since P and Q lie on AB and AC respectively:
- AB = AP + PB = 9 + x
- AC = AQ + QC = x + 4
Because PQ is drawn parallel to BC, the triangles APQ and ABC are similar.
This gives us the proportion: AP / AB = AQ / AC
9 / (9 + x) = x / (x + 4)
9(x + 4) = x(9 + x) 9x + 36 = 9x + x²
9x + 36 = 9x + x²
36 = x²
Therefore: x = √36 = 6
Since PB = x, PB = 6 units.
(ix) If cos θ + sec θ = 2, then determine the value of cos2024θ + sec2024θ.
Answer
cos θ + sec θ = 2
or, cos θ + 1\over \text{cos θ} = 2
or, cos² θ + 1 = 2cos θ
or, cos² θ – 2cos θ + 1 = 0
or, (cos θ – 1)² = 0
or, cos θ – 1 = 0
or, cos θ = 1 and sec θ = 1
Now, cos2024θ + sec2024θ = (1) 2024 + (1) 2024
= 1 + 1 = 2
(x) The lengths of two adjacent walls of a room are 12 m and 8 m respectively. If the height of the room is 4 m, determine the area of the floor of the room.
Answer
The two given walls that meet at a corner (12 m and 8 m) represent the length and width of the rectangular floor.
Length = 12 m and Width = 8 m
Area = 12 m × 8 m = 96 m²
The height of the room (4 m) is not needed to find the area of the floor. The height would be relevant if we were asked for the volume of the room, but for the floor area alone, only the length and width matter.
Therefore, the area of the floor is 96 m².
(xi) Curved surface area of a solid sphere is S and volume V, then find the value of S^3\over V^2.
Answer
Given a solid sphere with radius r, we know:
Surface area S = 4πr²
Volume V = (4/3)πr³
Now, S^3\over V^2.
= (4πr²)^3\over ({({4\over3})}πr³)^2
= 64π³r⁶\over {({16\over9})}π²r⁶
= 64π\over {({16\over9})}
= 64π × 9\over 16
= 36 π
(xii) If the mean of the data x1, x2, x3, …, x50 is x̄, then find the value of (x1 – x̄) + (x2 – x̄) + … + (x50 – x̄).
Answer
Given that the mean of x1, x2, x3, …, x50 is x̄, we know:
x̄ = (x1 + x2 + x3 + … + x50) / 50
Consider the sum: (x1 – x̄) + (x2 – x̄) + … + (x50 – x̄)
Distribute the summation: = (x1 + x2 + … + x50) – 50x̄
Since x̄ is the mean: x1 + x2 + … + x50 = 50x̄
Substitute this: = 50x̄ – 50x̄ = 0
Therefore, the value of (x1 – x̄) + (x2 – x̄) + … + (x50 – x̄) is 0.
Question – 5
Answer any One of the following Questions:
(i) Rohan takes a loan of ₹2,40,000 from a bank for constructing a building at the rate of simple interest of 12% per annum. After 1 year of taking the loan, he rents the house at the rate of ₹5200 per month. Determine the number of years he would take to repay his loan along with interest from the income of the house rent.
Answer
Let after x years he will repayment the amount.
Interest of ₹ 240000 at 12% for x years
= \frac{240000 × 12 × x}{100} = 28800 x
Amount = Principal + Interest
= ₹ (240000+28800x)
Now, house rent for 1 year 12m = ₹ 5200 × 12
∴ House rent for (x – 1) yrs = ₹ 5200 × 12 × (x – 1)
= 62400 (x – 1)
According to the problem,
62400 (x – 1) = 240000 + 28800 x
or, 62400 x – 62400 = 240000 + 28800 x
or, 62400 x – 28800 x = 240000 + 62400
or, 33600 x = 302400
∴ x =\frac{302400}{33600} = 9
∴ After 9 years he will repay his loan with interest.
(ii) Srikanta and Soifuddin have started a partnership business together by investing ₹30,000 and ₹50,000 respectively. After 6 months, Srikanta has invested ₹4,000 more but Soifuddin withdrew ₹1,000 for personal need. If the profit at the end of the year is ₹19,000, calculate the profit share of each of them.
Answer
Investment of Srikanta = ₹30,000 × 6 + ₹34,000 × 6
= ₹ 384,000
Investment of Soifuddin = ₹50,000 × 6 + ₹49,000 × 6
= ₹ 594,000
Ratio of investments = ₹ 384,000 : ₹ 594,000 = 64 : 99
Sum of ratio parts = 64 + 99 = 163
Srikanta’s share = 64\over163 × 19,000 = ₹ 7,460
Soifuddin’s share = 99\over163 × 19,000 = ₹ 11,540
Question – 6
Answer any One Question:
(i) Solve: x - 2\over x + 2 + 6 x - 2\over x - 6 = 1, [x ≠ -2, 6].
Answer
x - 2\over x + 2 + 6 x - 2\over x - 6 = 1
or, (x - 2)(x - 6) + 6(x - 2)(x + 2)\over (x + 2)(x - 6) = 1
or, (x² – 8x + 12) + 6(x² – 4) = x² – 4x – 12
or, 7x² – 8x – 12 = x² – 4x – 12
or, 7x² – 8x – 12 – x² + 4x + 12 = 0
or, 6x² – 4x = 0
or, 2x(3x – 2) = 0
or, x = 0 or x = 2/3
(ii) If one root of the equation ax² + 5x + c = 0 is twice the other, find the value of b²/ac.
Answer
Let the roots be α and 2α
Sum of roots = α + 2α = –5\over a
or, 3α = –5\over a
or, α = –5\over 3a — (1)
Product of root = α × 2α = c\over a
or, 2α² = c\over a
or, α² = c\over 2a — (2)
Put α = –5\over 3a
(-5\over 3a)² = c\over 2a
or, 25\over 9a² = c\over 2a
or, 25\over 9a = c\over 2
or, 50 = 9 ac
or, ac = 50\over9
Now, b^2\over ac = 5^2\over {50\over9}
= 9\over 2
Question – 7
Answer any One Question:
(i) If x = √7 + √3\over√7 - √3 and xy = 1, then calculate the value of x² + xy + y²\over x² - xy + y².
Answer
x = √7 + √3\over√7 - √3 × √7 + √3\over√7 + √3
= (√7 + √3)²\over (√7)² - (√3)²
= 7 + 2√21 + 3\over 7 - 3
= 10 + 2√21\over 4
= 5 + √21\over 2
and y = 1\over x = 5 - √21\over 2
Finding (x + y) :
x + y = 5 + √21\over 2 + 5 - √21\over 2
= 5
Finding x² + y²:
x² + y² = (x + y)² – 2xy
= (5)² – 2(1)
= 23
Now, x² + xy + y²\over x² - xy + y² = x² + y² + xy\over x² + y² - xy
= 23 + 1\over 23 - 1
= 24\over 22
= 12\over 11
(ii) If 3x – 4y ∝ √xy, then show that x² + y² ∝ xy.
Answer
(3x – 4y) ∝ √xy
or, (3x – 4y)² ∝ (√xy)²
or, 9x² – 24xy + 16y² ∝ xy
or, 9x² – 25xy + 16y² ∝ 0
or, 9x² – 16xy – 9xy + 16y² ∝ 0
or, x (9x – 16y) – y (9x – 16y) ∝ 0
or, (9x – 16y)(x – y) ∝ 0
or, (x – y) ∝ 0 —- (1)
Multiplying both sides by x + y
(x – y)(x + y) ∝ 0
or, (x + y) ∝ 0
We know, x³ + y³ = (x + y)(x² – xy + y²)
or, (x + y) = x³ + y³\over x² - xy + y²
or, x³ + y³\over x² - xy + y² ∝ 0
or, x³ + y³ ∝ 0
or, (x + y)(x² – xy + y²) ∝ 0
or, x² – xy + y² ∝ 0
or, x² + y² ∝ xy
Question – 8
Answer any One Question:
(i) If ay - bx\over c = cx - az\over b = bz - cy\over a, then prove that x\over a = y\over b = z\over c
Answer
ay - bx\over c = cx - az\over b = bz - cy\over a = k
or, ay - bx\over c = k
or, ay – bx = kc
or, ay - bx\over ab = kc\over ab
or, {y\over b} - {x\over a} = kc\over ab — (1)
cx - az\over b = k
or, cx – az = kb
or, cx - az\over ac = kb\over ac
or, {x\over a} - {z\over c} = kb\over ac — (2)
bz - cy\over a = k
or, bz – cy = ka
or, bz - cy\over bc = ka\over bc
or, {z\over c} - {y\over b} = ka\over bc — (3)
Adding (1), (2) and (3)
{y\over b} - {x\over a} + {x\over a} - {z\over c} + {z\over c} - {y\over b} = kc\over ab + kb\over ac + ka\over bc
or, kc\over ab + kb\over ac + ka\over bc = =
or, (a² + b² + c²)k\over abc = 0
or, k = 0 × abc\over (a² + b² + c²) = 0
From eq (1)
cx – az = kb
or, cx – az = 0 × b
or, cx = az
or, x\over a = z\over c —- (4)
From eq (2)
bz – cy = ka
or, bz – cy = 0 × a
or, bz – cy = 0
or, bz = cy
or, \text{b}\over \text{y} = \text{z}\over \text{c} —- (5)
From (4) and (5)
\text{x}\over \text{a} = \text{b}\over \text{ y} = \text{z}\over \text{c}
(ii) If a, b, c, d are in continued proportion, then prove that (b – c)² + (c – a)² + (b – d)² = (a – d)².
Answer
\text{a}\over \text{b} = \text{b}\over \text{c} = \text{c}\over \text{d} = k
c = dk
b = ck = dk²
a = bk = dk³
LHS: (dk² – dk)² + (dk – dk³)² + (dk² – d)²
= d²k²(k – 1)² + d²k²(1 – k²)² + d²(k² – 1)²
= d²{k²(k – 1)² + k²(1 – k²)² + (k² – 1)²}
= d²{k²(k² – 2k + 1) + k²(k⁴- 2k² + 1) + (k⁴- 2k² + 1)}
= d²(k⁴- 2k³ + k² + k⁶ – 2k⁴ + k² + k⁴- 2k² + 1)
= d²(k⁶ – 2k³ + 1)
= d²k⁶ – 2d²k³ + d²
= (dk³)² – 2(dk²)(d) + d²
= (dk³ – d)² = (a – d)² RHS (Proved)
Question – 9
Answer any One Question:
(i) Prove that the front angle formed at the centre of a circle by an arc is the double of the angle formed by the same arc at any point on the circle.
Answer
Given: ∠AOB is the angle at the center of the circle with center O, and ∠ACB is the angle at any point on the circle formed by the circular arc APB.
To Prove: ∠AOB = 2∠ACB
Construction: C, O are joined, and CO is extended up to the point D.
Proof:
In △AOC,
OA = OC in each case (radii of the same circle).
∴ ∠OCA = ∠OAC
Again, in each case, side CO of Δ AOC is extended up to point D.
Exterior ∠AOD = ∠OAC + ∠OCA = 2∠OCA — (I)
In ΔBOC
OB = OC in each case (radii of the same circle).
Again, since side CO of ΔBOC is extended up to point D:
∴ Exterior ∠BOD = ∠OCB + ∠OBC = 2 ∠OCB — (II)
∠AOD + ∠BOD = 2∠OCA + 2∠OCB
∴ ∠AOB = 2(∠OCA + ∠OCB) = 2∠ACB — (III)
∴ ∠AOB = 2∠ACB (Proved)
(ii) State and prove Pythagoras theorem.
Answer
Pythagoras Theorem: In any right-angled triangle, the area of the square drawn on the hypotenuse is equal to the sum of the areas of the squares drawn on the other two sides.
Given: ABC is a right-angled triangle whose ∠A is a right angle.
To prove: BC² = AB² + AC²
Construction: I draw a perpendicular AD on the hypotenuse BC from the right angular point A which intersects the side BC at the point D.
Proof: In right-angled Δ ABC, AD is perpendicular on the hypotenuse BC.
∴ Δ ABD and Δ CBA are similar.
Hence,
{\text{AB} \over \text{BC}} = {\text{BD} \over \text{AB}},
∴ AB² = BC × BD —- (i)
Again, ΔCAD and ΔCBA are similar.
Hence,
{\text{AC} \over \text{BC}} = {\text{DC} \over \text{AC}}
∴ AC² = BC × DC —- (ii)
So, by adding (i) and (ii), I get:
AB² + AC² = BC × BD + BC × DC.
= BC (BD + DC) = BC × BC = BC².
∴ BC² = AB² + AC² [proved]
Question – 10
Answer any One Question:
(i) In a triangle ABC, AB = AC and E is any point on the extended BC. If the circumcircle of ΔABC intersects AE at point D, prove that ∠ACD = ∠AEC.
Answer
In △ABC, AB = AC,
∴ ∠ABC = ∠ACB ………..(1)
Now, ABCD is a cyclic quadrilateral,
∴ ∠ABC + ∠ADC = 180°
or, ∠ACB + ∠ADC = 180° ……..(2) [from (1)]
Again, ∠ACB + ∠ACE = 180° ……..(3)
From (2) and (3), we get:
∠ACB + ∠ADC = ∠ACB + ∠ACE
or, ∠ADC = ∠ACE
or ∠DCE + ∠DEC = ∠ACD + ∠DCE
or ∠DEC = ∠ACD
∴ ∠ACD = ∠DEC
Hence, ∠ACD = ∠AEC.
(ii) The two medians BE and CF of ΔABC intersect each other at the point G and if the line segment FE intersects the line segment AG at the point O, then prove that AO = 3OG.
Answer
Contruction: Extent AG to Point D.
G is the centroid of Δ ABC. AD is a median
Proof: AG : GD = 2 : 1
\text{AG}\over \text{GD} = 2\over 1
or, \text{AO + OG}\over \text{OD - OG} = 2\over 1
or, 2 OD – 2OG = OA + OG
or, 2 OD – OA = 3OG —– (i)
In Δ ABD, OF || BD
\text{AF}\over \text{BF} = \text{AO}\over \text{OD}
or, \text{AF}\over \text{AF} = \text{AO}\over \text{OD}
or, 1 = \text{AO}\over \text{OD}
or, OD = OA
Put OD = OA
2 OA – OA = 3OG
or, OA = 3OG (Proved)
Question – 11
Answer any One Question:
(i) Draw an isosceles triangle with one angle 120° and equal sides of length 4 cm, then draw its circumcircle.
Answer
(ii) Draw a circle of radius 2.8 cm length. Then draw two tangents of the circle from the point outside the circle and is at distance of 7.5 cm from the centre.
Answer
Question – 12
Answer any Two Questions:
(i) If the sum of two angles is 135° and their difference is π/12, then determine the sexagesimal value and circular value of two angles.
Answer
A + B = 135º —- (1)
A – B = π/12 = 15º—- (2)
Adding (1) and (2)
(A + B) + (A – B) = 150º
or, 2A = 150º
or, A = 75º
Put A in equation (1)
A + B = 135º
or, 75º + B = 135º
or, B = 135º – 75º = 60º
In Degree, A = 75º and B = 60º
In Circular values, A = 5π/12 and B = π/3
(ii) If \text{sinθ}\over \text{x} = \text{cosθ}\over \text{y}, then show that sinθ – cosθ = \text{(x - y)}\over\text{√(x² + y²)}.
Answer
\text{sinθ}\over \text{x} = \text{cosθ}\over \text{y} = k
∴ sinθ = kx — (1) and cosθ = ky — (2)
Squaring and adding (1) and (2)
(kx)² + (ky)² = sin²θ + cos²θ
or, k²(x² + y²) = 1
or, k = 1\over \sqrt{\text{x}^2+\text{y}^2}
sinθ = x\over \sqrt{\text{x}^2+\text{y}^2} and cosθ = y\over \sqrt{\text{x}^2+\text{y}^2}
∴ sinθ – cosθ = \text{x - y}\over \sqrt{\text{x}^2+\text{y}^2}
(iii) If x tan 30° + y cot 60° = 0 and 2x – y tan 45° = 1, then calculate the value of x and y.
Answer
x 1\over √3 + y 1\over √3 = 0
or, x + y = 0 — (1)
2x – y tan 45° = 1
or, 2x – y = 1 — (2)
Adding (1) and (2) we get
3x = 1 ⇒ x = 1\over 3
Substitutuing x in equation (1)
x + y = 0
or, 1\over 3+ y = 0
or, y = –1\over 3
∴ x = 1\over 3 and y = –1\over 3
Question – 13
Answer any One Question:
(i) A house of 15 m height stands on one side of a park and from a point on the roof of the house the angle of depression of the foot of the chimney of brick kiln of the other side is 30° and the angle of elevation of the top of the chimney of brick kiln is 60°. Calculate the height of the chimney and the distance between the brick kiln and the house.
Answer
Height of House (AB) = 15 m
Total height of chimney (CE) = CD + DE
In Δ ABC,
tan 30° = AB/BC
or, 1/√3 = 15/BC
or, BC = 15√3 m
In fig, BC = AD = 15√3 m
In ΔADE,
tan 60° = DE/AD
or, √3 = DE/15√3
or, DE = 15√3 × √3 = 45 m
∴ Total height of the chimney = CD + DE
= 15 + 45 = 60 m (Ans)
(ii) From a point on the roof of a house of 11 meter height, it is observed that the angles of depression of the top and foot of lamp post are 30° and 60° respectively, calculate the height of the lamp post.
Answer
In ABC,
tan 60° = 11\over \text{y}
or, √3 = 11\over \text{y}
or, y = 11\over √3
In ADE,
tan 30° = \text{DE}\over \text{AD}
or, tan 30° = \text{11 - x}\over \text{y}
or, tan 30° =\text{11 - x}\over {11\over √3}
or, 1\over √3 = (11 - x)√3\over 11
or, 11 = (11 – x)√3 × √3
or, 33 – 3x = 11
or, 3x = 22
or, x = 22/3 = 7.33 m
Question – 14
Answer any One Question:
(i) The length of the radius of cross-section of a solid right circular rod is 3.2 cm. By melting the rod, 21 solid spheres are made. If the radius of the sphere is 8 cm, then determine the length of the rod.
Answer
Radius = 3.2 dcm = 32 cm
Length of rod = x cm (Let)
∴ the volume of the rod = π × (32)² × x
The radius of each sphere = 8 cm
∴ The volume of each sphere = 4\over 3 × π × 8³
So, the volume of 21 spheres = 21 × 4\over 3 × π × 8³
= 28 × 512π
ATP
π × (32)² × x = 28 × 512π
or, x = 28 × 512\over 32 × 32 = 14 cm
(ii) The quantity of iron sheet to make a body of right circular conical shape is 75 3\over7 m². If the slant height of it is 5 m, calculate the volume of the conical body and its height. Again determine the expenditure to colour the curved surface area of the buoy at the rate of ₹2.80 per m².
Answer
Slant height = 5 m
Radius of buoy = r m
∴ TSA of a buoy = 22\over 7r(r+5)
or, 22\over 7r(r+5) = 75 3\over7
or, 22\over 7r(r+5) = 528\over7
or, r(r+5) = 528 × 7\over7 × 22
or, r² + 5r = 24
or, r² + 5r – 24 = 0
or, (r + 8)(r – 3) = 0
∴ r = 3 or -8
Height of the buoy (h) = \sqrt{5^2-3^2} = √16 = 4 cm
(a) Volume of buoy = {1\over 3}×{22\over 7} × 3 × 3 × 4
= 37 {5\over 7} cm³
(b) Cost of colouring = 2.80 × 528\over7 = ₹ 211.20
Question – 15
Answer any Two Question:
(i) Calculate the mean from the following data:
Class | Frequency |
0 – 30 | 12 |
30 – 60 | 15 |
60 – 90 | 20 |
90 – 120 | 25 |
120 – 150 | 8 |
Answer
Class | Class mark (x) | f | fx |
0 – 30 | 15 | 12 | 180 |
30 – 60 | 45 | 15 | 675 |
60 – 90 | 75 | 20 | 1500 |
90 – 120 | 105 | 25 | 2625 |
120 – 150 | 135 | 8 | 1080 |
Total | ∑f = 80 | ∑fx = 6060 |
Mean = ∑fx\over ∑f = 6060\over 80 = 75.75
The mean of the given data is 75.75.
(ii) Find the median of data from the following frequency distribution table:
Marks obtained | Number of student |
Less than 10 | 8 |
Less than 20 | 15 |
Less than 30 | 29 |
Less than 40 | 42 |
Less than 50 | 60 |
Less than 60 | 70 |
Answer
Marks obtained | Frequency (f) |
CF |
10 – 20 | 8 | 8 |
20 – 30 | 7 | 15 |
30 – 40 | 14 | 29 |
40 – 50 | 13 | 42 |
50 – 60 | 18 | 60 |
60 – 70 | 10 | 70 |
Median Class = N\over 2 = 70\over 2 = 35th Observation
∴ Median Class = 40 – 50
Median = 40 + {70\over 2}- 29\over 13 × 10
= 40 + 35- 29\over 13 × 10
= 40 + 4.615 = 44.615
(iii) Find the mode of data from the following frequency distribution table:
Class Interval | Frequency |
0 – 5 | 2 |
5 – 10 | 6 |
10 – 15 | 10 |
15 – 20 | 16 |
20 – 25 | 22 |
25 – 30 | 11 |
30 – 35 | 8 |
35 – 40 | 5 |
Answer
The modal class is 20 − 25 with fm = 22.
Given:
- L = 20 (lower boundary of modal class)
- fm = 22 (frequency of modal class)
- f1 = 16 (frequency of previous class)
- f2 = 11 (frequency of next class)
- h = 5 (class width)
Mode = 20 + {22-16 \over 2 (22)-16-11} \times 5
= 20 + 1.7645 = 21.76
The mode of the given data is approximately 21.76.