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.
Basic Concepts: Divisibility rules, Prime factorization, Introduction to Exponents
Related Concepts: Applications of percents, Percents, fractions, and decimals

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?
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5.
Operations with Decimals
5.1
Adding and subtracting decimals
5.2
Multiplying decimals
5.3
Dividing decimals
5.4
Order of operations (PEMDAS)
ACCUPLACER Test Prep
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