Let's do one:

Does 3 go into 1620?  ( Is 1620 divisible by 3? )
 

1)  Add up the digits.  1 + 6 + 2 + 0 = 9


2 )  Does 2 go into 9? Yep!

So, 1620 is divisible by 3!  ( Grab a calculator to check or do some long division. )

 

Here's another one:

Does 3 go into 21,496?  ( Is 21,496 divisible by 3? )
 

2 + 1 + 4 + 9 + 6 = 22
 

01-divisibility-tests-22.gif

 

Take a look at all of the answers for your "threes" times tables!

3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36
 

Does the test work on all of them?