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# If (A – B): (A + B) = 1: 11, Find the Ratio (5a + 4b + 15): (5a – 4b + 3). - Mathematics

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#### Question

If (a – b): (a + b) = 1: 11, find the ratio (5a + 4b + 15): (5a – 4b + 3).

#### Solution

(a - b)/(a + b) = 1/11

11a - 11b = a = b

10a = 12b

a/b = 12/10 = 6/5

So let a = 6k and b = 5k

(5a + 4b + 15)/(5a  - 4b + 3) = (5(6k) + 4(5k) + 15)/(5(6k) - 4(5k) + 3)

= (30k + 20k + 15)/(30k - 20k + 3)

= (50k + 15)/(10k + 3)

= (5(10k + 3))/(10k + 3)

= 5

Hence (5a + 4b + 15):(5a - 4b + 3) = 5 : 1

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#### APPEARS IN

Selina Solution for Concise Mathematics for Class 10 ICSE (2020 (Latest))
Chapter 7: Ratio and Proportion (Including Properties and Uses)
Exercise 7(A) | Q: 4 | Page no. 87

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Solution If (A – B): (A + B) = 1: 11, Find the Ratio (5a + 4b + 15): (5a – 4b + 3). Concept: Ratios.
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