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.
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 |
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.
Mutiply the following numbers by four (Double the Double).
2
3
7
11
25
47
101
0.5
7.5
55.5
8
12
28
44
100
188
404
2
30
222
Thank you for reading.
