Decimal Numbers
Primary 4 · Mathematics
Decimal Numbers
Lesson 3 of 4
25 min
Let's begin
At the school sports day, four friends do the long jump. The teacher writes: Keza 2.4 m, Mugisha 2.45 m, Uwase 2.54 m, Gatete 2.05 m. Mugisha says, "I won, because 45 is the biggest number!" Is he right?
To compare decimals, write them one under the other with the decimal points in a line. If one number is shorter, add zeros at the end so they have the same number of places. A zero at the end of a decimal does not change its value: 2.4 = 2.40, because 4 tenths = 40 hundredths.
| Name | Ones | . | Tenths | Hundredths |
|---|---|---|---|---|
| Keza | 2 | . | 4 | 0 |
| Mugisha | 2 | . | 4 | 5 |
| Uwase | 2 | . | 5 | 4 |
| Gatete | 2 | . | 0 | 5 |
Compare the ones first. They are all 2. Next compare the tenths: Uwase has 5 tenths, which is the most. So Uwase jumped the furthest, not Mugisha!
Keza and Mugisha both have 4 tenths, so look at the hundredths: 0 < 5, so 2.40 < 2.45.
Order from the shortest jump to the longest: 2.05, 2.4, 2.45, 2.54.
Is 0.45 bigger than 0.5? No! Write 0.5 as 0.50. Then 0.45 has 4 tenths and 0.50 has 5 tenths, so 0.45 < 0.5. More digits does not mean a bigger decimal.
Tip
Points in a line, fill with zeros. Line up the decimal points, give every number the same number of places, then compare like whole numbers from the left.
Work each one in your exercise book first. Then tap Show answer to check.
Write <, > or = : 0.7 ___ 0.69
Answer: >. 0.70 has 7 tenths and 0.69 has only 6 tenths.
Write <, > or = : 3.07 ___ 3.7
Answer: <. 3.07 has 0 tenths and 3.7 has 7 tenths.
Write <, > or = : 1.5 ___ 1.50
Answer: =. A zero at the end does not change the value.
Put in ascending order: 0.8, 0.08, 0.75, 0.5
Answer: 0.08, 0.5, 0.75, 0.8
Two bottles hold 1.25 litres and 1.3 litres. Which holds more?
Answer: 1.3 litres, because 1.30 has 3 tenths and 1.25 has only 2 tenths.
What you learned today
Sources and credits
The stories, Rwandan worked examples, diagrams and practice questions were written by Ganzaa.
Quick check
Which sign goes in the gap? 0.6 ___ 0.58
