Multiplying By Four - Double The Double

Multiplying By Four - Double The Double

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Hi there. This math educational post is on multiplying by four. This topic is suitable for young mathematics learners and for those into fast mental math for multiplying by four.

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Review Of Doubles - Adding A Number By Itself

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Before getting into multiplying numbers by four, you can see doubling of numbers as adding a number by itself. As an example, double of two is four as two plus two is four. Double of 38 is 76.

A chart of numbers with its associated double can be found below.

Number	Double
1	2
2	4
3	6
4	8
5	10
6	12
7	14
8	16
9	18
10	20
11	22
12	24
13	26
14	28
15	30

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Double The Double For Multiplying By Four

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A nice and easy way of multiplying (whole) numbers by four is to double the number twice. A memory aid here would be to double the double.

Example One

What is 7 multiplied by 4?

Taking double of 7 is 14. To obtain 7 multiplied by 4 is taking the double of 14 which would be 28.

Example Two

What is 16 multiplied by 4?

Double of 16 is 32 and double of 32 is 64. The answer is 64.

Example Three

What is 37 multiplied by 4?

The double of 37 is 74 and double of 74 is 148.

Example Four (Fractions Case)

What is 3.5 multiplied by 4?

Double of 3.5 is 7 and double of 7 is 14.

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Practice Problems

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Mutiply the following numbers by four (Double the Double).

1. 2

2. 3

3. 7

4. 11

5. 25

6. 47

7. 101

8. 0.5

9. 7.5

10. 55.5

Answers To Practice Problems

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1. 8

2. 12

3. 28

4. 44

5. 100

6. 188

7. 404

8. 2

9. 30

10. 222

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Thank you for reading.