Question

The present ages of two students are in the ratio 5: 3. After 6 years, their ages
be in the ratio 7:5. The present age of the first student is
(c) 20 years
(d) 15 years
(a) 5 years
(6) 10 years​

Answer 1

Answer:

c) 20 years

Step-by-step explanation:

may it is helpful to u

Answer 2

let the present age of first student be x years and second student be y years

by the first given condition,

x/y=5/3

3x=5y

3x-5y=0----(1)

by the second given condition,

x+6/y+6=7/5

5(x+6)=7(y+6)

5x+30=7y+42

5x-7y=42-30

5x-7y=12---(2)

multiply eqn 1 by 7 & eqn 2 by 5

21x-35y=0----(3)

25x-35y=60----(4)

substract eqn 3 from 4

25x-35y =60

-

21x-35y=0

------------------------

4x=60

x=60/4

x=15

hence the present age of first student is 15 years