If 21y5 is a multiple of 9,where y is a digit,what is the value of y - Maths -

Question

If 21y5 is a multiple of 9,where y is a digit,what is the value of
y ?

Gopal Mohanty · Accepted Answer

If a number is a multiple of 9, then the sum of its digits will
be divisible by 9
Sum of digits of 21y5 = 2 + 1 + y + 5 = 8 +
y
Hence, 8 + y should be a multiple of 9
This is possible when 8 + y is any one of these numbers
0, 9, 18, 27, and so on …
However, since y is a single digit number, this sum can
be 9 only Therefore, y should be 1 only

If 21y5 is a multiple of 9,where y is a digit,what is the value of y ?