How to check math multiplication - cast out nines trick

Casting out nines is a fast and easy method of making sure your math multiplication calculations are correct. This trick involves adding the digits of each number and reducing each to a single digit, then comparing the end result with the answer. To donate to the tecmath channel: https://paypal.me/tecmath?locale.x=en_AU To donate to the tecmath channel: https://paypal.me/tecmath?locale.x=en_AU
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