Multiplication
INSTANT MULTIPLICATION Multiplication Let’s begin with one of my favorite feats of mental math—how to multiply, in your head, any two-digit number by eleven. It’s very easy once you know the secret. Consider the problem: 32 x 11 To solve this problem, simply add the digits, 3 + 2 = 5 , put the 5 between the 3 and the 2, and there is your answer: 3 5 2 What could be easier? Now you try: 53 x 11 Since 5 + 3 = 8, your answer is simply 583 One more. Without looking at the answer or writing any-thing down, what is 81 x 11 ? Did you get 891? Congratulations! Now before you get too excited, I have shown you only half of what you need to know. Suppose the problem is 85 x 11 Although 8 + 5 = 1 3 , the answer is NOT 8 13 5! As before, the 3 goes in between the numbers, but the 1 needs to be added to the 8 to get the correct answer: 9 3 5 Think of the problem this way: