Start with a deck of cards. Before the trick, sneak a peek at the 10th card in the deck. Memorize it. Ask your volunteer to add the first and second digit of their number together. For instance, if he ...

Add Yahoo as a preferred source to see more of our stories on Google. This math trick can help you multiply any two-digit number by 11. Arlene Resendiz is TikTok’s resident math whiz. When she’s not ...