1. Decimals
Objective: Be able to add, subtract, multiply and divide simple decimal numbers without using a calculator
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2. It’s a good idea to write in any missing noughts
Adding and Subtracting When we add or subtract decimal numbers, we must keep the decimal points in line. Here is an example of adding 2.56 and 0.324
2.56 +
0.324
Keep the decimal points in line
Add up keeping the decimal point in line
2.884

3. Subtracting In the same way, we must keep the decimal points in line when subtracting decimals. Here is an example of subtracting 2.06 and from 3.78
3.78 -
2.06
Take away keeping the decimal point in line
Keep the decimal points in line
1.72

4. Try these
= 5.79
= 9.41
= 4.683
= 3.258
= 3.13
= 3.452
= 9.711
= 5.271

5. Multiplying Decimals
The chances are that you will be allowed to a calculator for multiplications like:
2.346 x 7.067
But on the non-calculator paper, sometimes simple divisions like 0.3 x 0.02 cause problems. Here is how to do it…

6. We can change the decimals into whole numbers by multiplying by 10
This makes it a whole number multiplication that we can do . 3 x 02
x 10
x 100 3 x 2 6
Now, we undo the x 10 x 100 which is x 1000 with ÷1000
6 ÷ 1000 = 0.006

7. 1. . 4 x 3 2. . 3 x 5 3. . 8 x 4 4. . 4 x 7
0.12
0.15
0.32
0.28 5. . 9 x 03 6. . 2 x 1 7. . 3 x 2 8. . 3 x 1
0.027
0.02
0.06
0.03 9. . 02 x 4
10. . 2 x 02
11. . 3 x
12. . 1 x
0.008
0.004
0.09
0.01

8. Multiply the divided number by the same power of 10
The divisor must be a whole number
0.12 ÷ 0.2
1.2 ÷
x 10 2
x 10
Multiply by the power of 10 that makes it a whole number 6 2 1 . 1
Ans 0.6
Keep decimal points in line

9. The divisor must be a whole number
0.032 ÷ 0.08
3.2 ÷
x 100
x 100 8
Multiply the divided number by the same power of 10
Multiply by the power of 10 that makes it a whole number
Now, the divisor is a whole number and we can divide 4 8 3 . 2 3
Ans 0.4
Keep decimal points in line

10. Try these 1.
2.4 ÷
0.2 2.
4.5
0.5 3.
2.1
0.3 4.
0.75 5.
3.75 6.
8.88
0.04 7.
0.034 8.
2.04
0.004
= 12
= 9
= 7
= 1.5
= 7.5
= 222
= 0.17
= 510