Question

4 years ago, the ratio of the ages of A and B was 2: 3 and after 4 years it becomes 5 : 7. Find the
present ages.

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Answer 1

Answer:

step by step explaination:

Let the present age of A and B be A and B respectively.

Given thatA−4B−4=35A−4B−4=35 -> (i)(Before 4 years)

and A+4B+4=57A+4B+4=57 -> (ii)( After 4 years)

Cross multiplying equation

 (i) gives

5A−20=3B−125A−20=3B−12

i.e 5A−3B=85A−3B=8

 ->(iii)

And cross multiplying

 (ii) gives

7A+28=5B+207A+28=5B+20

i.e 7A−5B=−87A−5B=−8->

(iv)

Now substituting equation (iv) in (iii) we get

5A−3B=−(7A−5B)5A−3B=−(7A−5B)

i.e 5A−3B=5B−7A5A−3B=5B−7A

i.e 12A=8B12A=8B

Therefore A:B = 2:3

Their present ages are in the ratio 2:3

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Answer 2

Step-by-step explanation:

present age :

A= 2x+4,

B= 3x +4

{2x+4+4 }/ {3x+4 +4 } =5/7

{ 2x+8 }/ 3x+8 = 5/7

14x + 56 = 15x +40

x = 16

present age:

A= 32 + 4 = 36

B= 48 + 4 = 52