In the previous post I have given to you 5 tricks,, and this are the rest....
- Square numbers in the 50’s
58 x 58 = 3364
Step 1. Add
25 to the ones digit : 25 + 8 = 33
Step 2. Square the ones digit number : 8 x 8 = 64
Step 3. Place the result from step 2 next to the
result from step 1 : 3364
- Multiply two digit numbers having same tens digit and ones digits add to 10
38 x 32 = 1216
Step 1. Multiply the first digit by the first
digit plus one: 3 x (3 + 1) = 12
Step 2. Multiply the rightmost digits (if the
result is a single digit put a 0 in front of it) : 8 x 2 = 16
Step 3. Put the result from step 2 next to the
result from step 1: 1216
- Multiply by 9, 99, 999, etc.
56 x 99 = 5544
Step 1. Place a zero at the end for each 9 : 5600
Step 2. Subtract the original number from step 1:
5600 – 56 = 5544
- Multiply by 125
68 x 125 = 8500
Step 1. Place three zeros at the end of the number
68000
Step 2. Divide the number from step 1 by two:
68000/2 = 34000
Step 3. Divide the number from step 2 by two:
34000/2 = 17000
Step 4: divide the number from step 3 by two:
17000/2 = 8500
8 x 125 = 1000
Step 1. Place three zeros at the end of the number
68000
Step 2. Alternatively, divide the number from step
1 by eight: 8000/8 = 1000
- Square numbers if you know the square of the previous number
61 x 61
Step 1. Find the square of the previous number 60
x 60 = 3600
Step 2. Multiply the number being squared by two
and subsract one: (61 x 2) – 1 = 121
Step 3. Add step 2 to step 1: 3600 + 121 = 3721
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