# Adding and subtracting decimals

### Adding and subtracting decimals

In this section, we will add and subtract decimal numbers. The process of adding and subtracting decimal numbers is the same as adding and subtracting whole numbers. For example, both involve regrouping. After lining up the decimals, you will sometimes have to add one or more zeroes to a number after the decimal point. Being able to add and subtract decimal numbers is an important life skill, especially when dealing with money and purchases.

#### Lessons

• Introduction
a)
i) How to add decimals?
ii) How to subtract decimals?

b)
How to round decimals?

• 1.
Evaluate. Then, round your answer to the nearest tenth.
a)
62.04 – 31.03

b)
98 + 38.97

c)
675.92 – 324.7

d)
30.5 – 40

• 2.
The table shows the approximate lengths of some dinosaurs.
 Dinosaur Height Dryosaurus 6.52ft Chasmosaurus 6.2ft Ankylosaurus 7.22ft Dravidosaurus 4.1ft
a)
Find the difference in length between the longest and shortest dinosaur.

b)
Arrange the dinosaurs in order from shortest to longest.

c)
How much longer is the Ankylosaurus than the Dryosaurus?

• 3.
Anna went to a store to buy some strings for an art project. She needs four pieces of string with lengths 14 cm, 15.61 cm, 12.55 cm, and 11.3 cm. Each pack of string has a total length of 25 cm. How many packs of string does she need to complete her project?