Question

If 4xy7 is exactly divisible by 3, then the least value of (x + y) is

(a) 1

(b) 4

(c) 5

(d) 7

Answer 1

4xy7 is exactly divisible by 3

$\therefore$ The sum of its digits must be divisible by 9

or 4 + x +y + 7 or 11 + (x +y) is divisible by 9

$\therefore$ Least value of x + y = 7

as 11 + 7 = 18 is divisible by 9 (d)