Question

Mathematics for Class 8
The ages of A and B are in the ratio 5:7. Four years from now the ratio of their ages will be
3:4. The present age of B is
(a) 20 years
(b) 28 years
(c) 15 years
(d) 21 years​

Answer 1

Answer:

THE CORRECT OPTION IS (B)28 YEARS...

Step-by-step explanation:

Let the common multiple be x.

So, age of A = 5x

age of B = 7x

Now, after 4 years their ages will be,

age of A = 5x + 4

age of B = 7x + 4

Now,

5x + 4 = 3

7x + 4 4

4(5x + 4) = 3(7x + 4).... [by cross multiplication]

20x + 16 = 21x + 12

21x - 20x = 16 - 12

x = 4

So present age of B = 7x = 7(4) = 28 years