QQuestion
What number must be added to each of the numbers 4, 6, 8 and 11 so that the resulting four numbers are in proportion?
✓Answer
Let x be added to each number.
The resulting numbers are 4 + x, 6 + x, 8 + x and 11 + x.
Since they are in proportion:
⇒ \frac{4+x}{6+x}=\frac{8+x}{11+x}
⇒ (4 + x)(11 + x) = (8 + x)(6 + x)
⇒ 44 + 4x + 11x + x² = 48 + 8x + 6x + x²
⇒ 44 + 15x + x² = 48 + 14x + x²
⇒ 15x − 14x = 48 − 44
⇒ x = 4
Therefore, the required number is 4.
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