Question

Find the digit that makes _2,530 divisible by 9

a.6
b.5
c.7
d.8

Answer 1

for a no to be divisible by 9 its individual digits should sum up to a no divisible by 9

Answer 2

you have to do trial and error by replacing the values as indicated by the choices..
anyone knows how to do it not using trial and error?

Answer 3

since 10^n = 1 (mod 9)

then: a10^k + b10^(k-1) + ...+m10^0 = a(1) + b(1) + ...+m(1) (mod 9)

Answer 4

try and see is the best method at the moment:

Answer 5

say if sum of digits =9 or 18 or 27 etc the num should be divisible by 9

Answer 6

haha yeah ryt