Question

If x7y5 is exactly divisible by 3, then the least value of (x + y) is 

A. 6 

B. 0 

C. 4 

D. 3

Answer 1

We know that if sum of digits of a number is divisible by 3, then the number is divisible by 3. 

Here, 

x + 7 + y + 5 = multiple of 3 

x + y + 12 = 0, 3, 6, 9, …. 

Hence, 

x + y + 12 = 12 

∴ x + y = 0 

But x + y cannot be 0 because then x and y both will have to be 0.Since x is the first digit, it cannot be 0.

∴ x + y + 12 = 15 x + y = 3 

∴ the least value of (x + y) is 3