WBBSEClass XMathematicsRatio And Proportion03 Mark2023 Moderate

QQuestion

If the fourth and fifth of the five numbers in continued proportion are 54 and 162 respectively, find the first number.

Exam-ready answer • 03 Mark

Answer

Let the continued proportion be a, ak, ak², ak3, ak4

Given: ak3 = 54 — (1) and  ak4 = 162— (2)

Dividing (2) and (1)

k = 3

Put k in eq (1)

ak3 = 54

or, a × 33 = 54

or, a × 27 = 54

or, a = 2

So, first number will be ‘2′.

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