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# If A, B and C Are in Continued Proportion, Prove That: A: C = (A2 + B2) : (B2 + C2) - ICSE Class 10 - Mathematics

#### Question

If a, b and c are in continued proportion, prove that: a: c = (a2 + b2) : (b2 + c2)

#### Solution

Given a, b and c are in continued proportion

=> a : b = b : c

Let a/b = b/c = k (say)

=> a = bk, b = ck

Now L.HS = a/c = ck^2/c = k^2

R.HS = (a^2 + b^2)/(b^2 + c^2)

= ((ck^2)^2 + (ck)^2)/((ck)^2 + c^2)

= (c^2k^2(k^2 + 1))/(c^2(k^2 + 1))

= k^2

LHS = RHS

Is there an error in this question or solution?

#### APPEARS IN

Selina Solution for Selina ICSE Concise Mathematics for Class 10 (2018-2019) (2017 to Current)
Chapter 7: Ratio and Proportion (Including Properties and Uses)
Ex.7D | Q: 13

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Solution If A, B and C Are in Continued Proportion, Prove That: A: C = (A2 + B2) : (B2 + C2) Concept: Proportions.
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