Speed Mathematics (secret skills for quick calculation) by Bill Handley
By using the same method, we can multiply numbers greater than 10.
Let's try an example:
96 x 97 =
What do we take these numbers up to? How many more to make what? One hundred. So we write 4 under 96 and 3 under 97.
What do we do now? We take away diagonally. 96 minus 3 or 97 minus 4 equals 93. This is the first part of your answer. What do we do next? Multiply the numbers in the circles. Four times 3 equals 12. This is the last part of the answer. The full answer is 9312.
Which method is easier, this method or the method you learned in school? This method, definitely.
Hope this's useful for you. More methods will be appear in the next post! ^^
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