Question

Solve this:

Find the positive integral solution of 13 x + 15 y = 189 , for which the value of y is largest.

Answer 1

13x + 15y = 189

Therefore 15y = 189 – 13x

When y is largest, x must have the least possible value.

15y is divisible by 15. Hence R.H.S. of the equation also should be divisible by 15.

The least value of x for which R.H.S. is divisible by 15 is x = 3

When x = 3; 15y = 189 – 13(3) = 189 – 39 = 150

i.e. 15y = 150; or y = 10

Hence, the required solution is x = 3; y = 10