Question

14. 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
(c) 15 years
b) 28 years
(d) 21 years
(a) 20 years
is 16 cm. Length of each of the​

Answer 1

Answer:

Present age of B = 28 years

Step-by-step explanation:

We know that,

A : B = 5 : 7

Let A = 5x and B = 7x

then, After 4 years their ages will be,

A(after 4 years) = 5x + 4

B(after 4 years) = 7x + 4

Now, their ratio = 3 : 4

(5x + 4) : (7x + 4) :: 3 : 4

We know that, In Proportionality

Product of extremes = Product of means

4 × (5x + 4) = 3 × (7x + 4)

Using Distributive property,

x(y + z) = xy + xz

= 4 × 5x + 4 × 4 = 3 × 7x + 3 × 4

= 20x + 16 = 21x + 12

= 21x - 20x = 16 - 12

= x = 4

Thus, their present age is A = 5(4) = 20 and B = 7(4) = 28

Hence, the present age of A is 20 years and B is 28 years

Hope it helped and you understood it........All the best