Question

Which of the following is a 4-digit number divisible by 3, 9, 5, and 10?

A.1360
B.2770
C.4800
D.9900

Answer 1

all numbers which are divisible by 9 have the property that all their digits add up to nine (just keep adding till you get to a single digit)

only one of those numbers meets this - so must be the answer

Answer 2

a quick way to find if a number is divisible by 3 is to add up the digits until you get a single digit - if this number is divisible by 3 then the original number is also.

Answer 3

@welshfella

that is of course a corollary of the 'divides by 9' rule above, since 9 divides by 3