This shortcut helps you multiply two numbers together. To use the shortcut, the numbers (1) must start with the same digit; and (2) the sum of the ones digits must be 10.

Problem: 33 x 37 =  ???? 

Here's how you do it:

1. Multiply the tens digit by one greater than the tens digit (in this case, 3 x 4 = 12). Write down the result.

33 x 37 =  12?? 

2. Then, multiply the ones digits together and write the result next to the first part.

33 x 37 = 1221  

One note: if the ones digits are 1 and 9, you need to write 09 in the answer, not just 9.

It's really easy once you get the hang of it. Be sure you check that the number fits the rule (tens digits match, ones digits add up to ten) before you use the shortcut!