Question

the ratio of the present age of two brothers is 4:5.After 10 years 'the ratio of their ages would be 6:7.find the age of the elder brother after 15 years

Answer 1

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Here's your answer...

Let the brothers' ages be x and y.

Then x:y = 4:5
By cross-multiplication...
5x=4y
5x-4y = 0

After 10 years, their ages will be x+18 and y+10
(x+10):(y+10) = 6:7
By cross-multiplication...
7x+70 = 6y+60
7x-6y+10 = 0

Multiplying the first equation by 3 and the sexond equation by 2 and subtracting ...

15x-12y = 0
14x-12y = -20
-.... +........ +
__________
x = 20

5×20 = 4×y
y = 25

The elder brother is 25 years old now, so after 15 years he will be 40 years old.

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Answer 2

Hey !!


Let present age of two brothers be 4x and 5x.


After 10 years age of two brothers = ( 4X + 10 ) and ( 5X + 10 ).




According to the question,

4x + 10 / 5x + 10 = 6/7


7 ( 4x + 10 ) = 6 ( 5x + 10 )


28x + 70 = 30x + 60



30x - 28x = 70 - 60


2x = 10


x = 5


Present age of two brothers = ( 4x ) and 5x = 4 × 5 and 5 × 5 = 20 years and 25 years.





Age of elder brother after 15 year's = 25+15 = 40 years.