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You can use these shortcut tricks for your kids school math if school teachers allow your kids to use it. In school maths, we learn the math in detailed way. We need to show the entire procedure of solving a math problem. So, if your school allow your kids to solve maths using shortcut, then you are good to go with it.
But, We recommend you to teach your kids both the ways. Use the long way for schools and learn the shortcut for your kids future.