Question:
Tick (✓) the correct answer
If x4y5z is exactly divisible by 9, then the least value of (x + y + z) is
(a) 3
(b) 6
(c) 9
(d) 0
Solution:
(c) 9
A number is divisible by 9 if the sum of the digits is divisible by 9.
$x+4+y+5+z=9+(x+y+z)$
The lowest value of $(x+y+z)$ is equal to 0 for the number x4y5z to be divisible by 9 .
In this case, all x, y and z will be 0.
But x is the first digit, so it cannot be 0.
∴ x+4+y+5+z = 18
or x+y+z+9 = 18
or x+y+z = 9