# What is the Value of A?

If A and B are in the ratio 4:5 and the difference of their squares is 81, what is the value of A?

- 15
- 12
- 36
- 45

**Answer: (3) 36**

**Explanation:-
**The ratio of A and B = 4: 5

Let the value of A and B be 4X and 5X.

The difference of their squares is 81,

Then, (5X)^{2} – (4X)^{2} = 81

X^{2} = 81

Square root on both sides,

X = 9

Then, the value of A = 4 X = 4 x 9

= 36

Hence, the answer is (3) 36.