Adding and Subtracting decimals

Adding and Subtracting decimals means doing addition and subtraction of decimal numbers. We have seen in the previous article the addition and subtraction of positive numbers, negative numbers, and whole numbers. In this article, we will see the addition and subtraction of decimal numbers.

Adding and Subtracting decimals: Adding decimals

To add the decimal numbers we need to align the decimal points of the number and then add.

For example, if you want to 0.4 + 1.3

0.4

1.3

Now do the addition, 0.4 + 1.3 = 1.7

Subtracting decimals

Similarly, for subtraction, we need to align the decimal points and then subtract.

For example, if you want to subtract 1.8 – 0.5

1.8

0.5

thus on subtracting, we get 1.8 – 0.5 = 1.3

Another example of addition and subtraction,

314.5 + 0.076 is equal to 314.500 + 0.076, aligning decimals and placing zeros after 5 in 314.5 to avoid mistakes while doing addition.

314.5 – 0.076 is equal to 314.500 – 0.076, aligning decimals and placing zeros after 5 in 314.5 to avoid mistakes while doing subtraction

Note: If you forget to place zero placeholders (In this case after 5), this will result to incorrect result.

The same rules that we applied for addition/subtraction of integers also apply to decimal numbers. So when you compute –0.076 + 314.5, you notice the one number is negative and one is positive, so you first subtract the small number from the larger number, 314.5 – 0.076, which is 314.424; then, because the sign of the larger number is positive, we assign a positive sign to the answer.

Examples For practice (taken from math book)

1. 3.1 + 0.06
2. 7.2 – 4.008
3. 6.5 – 8.49
4. 2.017 – 3
5. -7.75 – 9.1
6. 1.07 – 25
7. -14.48 + 29.7
8. 318.15 – 21.38
9. 3.99 – 3.990
10. 4.09 – 4.99