# Find the Value of the Product of x and Y

If 5x+9y=5 and 125x^{3}+729y^{3}=120 then the value of the product of x and y is:

- 45
- 135
- 1/9
- 1/135

**Answer : (4) 1/135**

**Explanation:-
**5x + 9y = 5 ……………….. (1)

Cube on both side,

(5x + 9y)

^{3}= 5

^{3}

(5x)

^{3}+ (9y)

^{3}+ 3 x 5x X 9y (5x + 9y) = 125

125x

^{3}+ 729y

^{3}+ 135 xy (5) = 125

Put the value of 125x

^{3}+ 729y

^{3}= 120 (Given in the question)

Then, 120 + 135 x 5 xy = 125

675 xy = 125 – 120

xy = 5/675

xy = 1/135

Then, the value of the product of x and y is 1/135.

Hence, the answer is (4) 1/135.