There's something about math tricks that just make math more interesting to kids. I find it a great sneaky way to add in that extra bit of math in a day without the groans!
Here is another cool math trick that I would like to share, it's one where your answer will always be 37! Of course, if the calculations are done correctly. If the answer is not 37, then a mistake has happened somewhere along the way.
Step 1: Think of a three digit number where all of the digits are the same, e.g. 111, 222, 333, 444.
For example I'm going to choose 777.
Step 2: Add the three digits together
For my example (777) 7 + 7 + 7 = 21
Step 3: Divide the number that you came up with in Step 1 by the result you ended up with in Step 2. (So Long Division Skills are needed here. For younger students you may wish to allow them to use a calculator if this is too difficult.)