Count Trick

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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 © Aidia Propitious

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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 a2

Tens

Ones

a2

2 a.b

2 a.b

b2

b2

For example:

132 = …

a=1



Hundreds 12 2 (1)(3)

; Tens

Ones

1 6

32 Result

b=3

9 169

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372 = …

a=3



Hundreds 32

9

2 (3)(7)

4

b=7

Tens

Ones

2

72 Sum

;

13

Result

4

9

6

9

1369

8. Quadrates of hundreds Separate hundreds into two part, tens (first 2 numbers) and ones (the last number) For example:

1022 = …

102

a = 10



;

b=2

Ten Thousands

Thousands

Hundreds

1

0

0

2 (10)(2)

4

Tens

0

22 Sum Result

Ones

4 1

0

4

0

4

10404

Good Luck !!

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