If the 8-digit number is 789x 531y is divisible by 72, then the value of (5x — 3y) is?Options-1210

The number 72 is a product of 8 and 9. For a number to be divisible by 72, it must be divisible by both 8 and 9.

1. For a number to be divisible by 8, the last three digits must be divisible by 8. So, 31y must be divisible by 8. The possible values of y are 2, 6.

2. For a number to be divisible by 9, the sum of all digits must be divisible by 9. So, 7+8+9+x+5+3+1+y must be divisible by 9. If y=2, x=5 to make the sum 45 which is divisible by 9. If y=6, there is no integer value of x that makes the sum divisible by 9.

So, y=2 and x=5.

3. Substituting these values into the expression 5x - 3y gives 55 - 32 = 25 - 6 = 19.

So, the value of (5x - 3y) is 19.