Quick: What's 92 x 94?

Anyone can be good at math with Mike Byster's shortcuts:

Shortcut #1: Squaring numbers in the 50s:

Example: 56 x 56:

Step 1: Start out with 25 and add the ones digit to it. 25 + 6 = 31

Step 2: Square the ones digit. 6 x 6 =36 Tack this onto the end of the answer from step 1.

Answer: 56 x 56 = 3,136

Now, if the number from step 2 is less than 10, you have to put a zero in front of it. So, if it is 53 x 53:

Step 1: 25 + 3 = 28

Step 2: 3 x 3 = 09 (note that since 9 is smaller than 10 we have to put a zero in front of it)

Answer: 53 x 53 = 2,809

Shortcut 2: Multiplying two numbers in the 90's together:

When you multiply two numbers in the 90's together, in parenthesis next to each number put how far that number is away from 100. Since 92 is 8 away from 100 and 94 is 6 away from 100, the problem 92 x 94 would look like this: 92 (8) x 94 (6)

Example: 93 (7) x 96 (4)

Step 1: Add up the numbers in parenthesis 7 + 4 = 11 and subtract that number from 100. 100 - 11 = 89

Step 2: Multiply the two numbers in parenthesis together and tack that on to the number from Step 1. 7 x 4 = 28

Answer: 93 x 96 = 8,928

Shortcut 3: Adding Trick

This is one of my favorite tricks, because it is simple and amazes anyone who sees it. Have someone pick two numbers below 10 and write one on top of the other. Have the person add them up and put the answer right below the two numbers. Have the person continue to add the bottom two numbers in the column, and keep on putting the total below it until you have ten numbers total. Then have him add up the entire column. Example: someone picks the numbers 4 and 7, and writes the 4 on top of the 7. The next number in the series would be 11. because 4 + 7 = 11. Then by adding the bottom two numbers in the column, the next number would be 18, because 7 + 11 = 18. The next number would be 29, because 11 + 18 = 29. He should keep doing that until he has ten numbers total, and then he adds up the entire column. The column could look something like this:

4

7

11

18

29

47

76

123

199

322

You will quickly glance at the numbers and tell him what all ten numbers add up to. The trick is to look at the seventh number on the list which in this case is 76. And then multiply that number by 11 and that is the total of the column. 76 x 11 = 836. You might say to yourself, I can't multiply by 11, but it is very simple. All you have to do is look at 76 and add the tens digit to it, 76 + 7 = 83. Then tack on the ones digit of 76 onto the end. Then it becomes 836.

If the seventh number was 34, you would add 34 + 3 = 37 and tack on the 4 at the end so it would be 374.

If the person picked two high numbers like 8 and 9, the seventh number could end up to be a three digit number. The column would look like this:

8

9

17

26

43

69

112

181

293

474

The seventh number in this case is 112. Then you would add the first two digits of 112 to itself. 112 + 11 = 123. Then put the ones digit of 112 onto the end of 123 and you get 1232, which is the sum of the ten numbers in the above example.

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