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COUNT TRICK
1. Multiplication by 5
It's often more convenient instead of multiplying by 5 to multiply
first by 10 and then divide by 2.
For example:
137 x 5 = …
137 · 10 = 1370 / 2 = 685
2. Division by 5
Similarly, it's often more convenient instead to multiply first by 2
and then divide by 10.
For example:
1375 : 5 = …
1375 . 2 = 2750 / 10 = 275
3. Division/multiplication by 4
Replace either with a repeated operation by 2.
For example:
124 : 4 = …
124 / 2 = 62 / 2 = 31
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124 x 4 = …
124 · 2 = 248 · 2 = 496
4. Division/multiplication by 25
Use operations with 4 instead.
For example:
3750 : 25 = …
3750 . 2 = 7500 . 2 = 15 000 / 100 = 150
37 x 25 = …
37 · 100 = 3700 / 2 = 1850 / 2 = 925
5. Division/multiplication by 8
Replace either with a repeated operation by 2.
For example:
124 x 8 = …
124 · 2 = 248 · 2 = 496 · 2 = 992
1240 : 8 = …
1240 : 2 = 620 : 2 = 310 : 2 = 155
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6. Division/multiplication by 125
Use operations with 8 instead.
For example:
1625 : 125 = …
1625 . 2 = 3250 . 2 = 6500 . 2 = 13 000 / 1000 = 13
37 x 125 = …
37 · 1000 = 37 000 / 2 = 18 500 / 2 = 9250 / 2 = 4625
7. Quadrate of tens
Tens gives symbol “a” and ones gives symbol “b”.
Hundreds Tens Ones
a2 a2
2 a.b 2 a.b
b2 b2
For example:
132 = …  a=1 ; b=3
Hundreds Tens Ones
12 1
2 (1)(3) 6
32 9
Result 169
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372 = …  a=3 ; b=7
Hundreds Tens Ones
32 9
2 (3)(7) 4 2
72 4 9
Sum 13 6 9
Result 1369
8. Quadrates of hundreds
Separate hundreds into two part, tens (first 2 numbers) and
ones (the last number)
For example:
1022 = …  a = 10 ; b=2
Ten
Thousands Hundreds Tens Ones
Thousands
102 1 0 0
2 (10)(2) 4 0
22 4
Sum 1 0 4 0 4
Result 10404
Good Luck !!
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