Decimal Numbers
Primary 4 · Mathematics
Decimal Numbers
Lesson 1 of 4
25 min
Let's begin
Byiringiro's father sells cloth at Kimironko market. A customer asks for "one and a half metres". Byiringiro sees the number 1.5 m on his father's notebook. What does the ".5" mean? It is a part of a metre, written as a decimal.
Cut one whole into 10 equal parts. Each part is one tenth: 110. We can also write one tenth as a decimal: 0.1.
The dot is called the decimal point. It separates the whole numbers (on the left) from the parts (on the right). 1.5 m means 1 whole metre and 5 tenths of a metre, which is one and a half metres.
Between 0 and 1 there are 10 equal jumps of 0.1:
0.3 is three jumps from 0, and 0.7 is seven jumps from 0. Between 2 and 3 it works the same way: 2.4 is four tenths past 2.
Cut one whole into 100 equal parts. Each part is one hundredth: 1100 = 0.01.
The grid shows 37100 = 0.37. Each column is one tenth (10 hundredths), so 0.37 is the same as 3 tenths and 7 hundredths.
We read 0.37 as "zero point three seven". We say each digit after the point on its own.
Tip
One place after the point is tenths; two places is hundredths. 0.3 = 310, and 0.37 = 37100.
Work each one in your exercise book first. Then tap Show answer to check.
Write 910 as a decimal.
Answer: 0.9
Write 0.45 as a fraction.
Answer: 45100
On a number line from 0 to 1 in tenths, what number is 6 jumps from 0?
Answer: 0.6
Which decimal is halfway between 0.4 and 0.6?
Answer: 0.5
How many hundredths make one whole?
Answer: 100. The grid has 100 small squares.
What you learned today
Sources and credits
Siyavula writes decimals with a comma (0,3); this lesson uses the decimal point (0.3). The stories, Rwandan worked examples, diagrams and practice questions were written by Ganzaa.
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