Discover Mathematics P4: Term 2, Unit 10, Lessons 1–4
GoalWrite tenths as fractions and as decimals, and place them on a number line.
New words
decimal · a number written with a decimal point, such as 0.3 or 1.4decimal point · the dot that separates the whole numbers from the partstenth · one of 10 equal parts of a whole; 1/10 = 0.1
Explanation
Fractions with denominator 10 can be written as decimals. A whole cut into 10 equal parts has tenths. One tenth is 1/10 and we write it as 0.1. The dot is the decimal point; the digit after it tells how many tenths. So 3/10 = 0.3 and 7/10 = 0.7. Ten tenths make one whole: 10/10 = 1.0 = 1. On a number line from 0 to 1 with 10 equal steps, 0.3 is the third step. Numbers bigger than 1 work in the same way: 1.4 means one whole and 4 tenths, 1 4/10. Read 0.3 as three tenths. The digit before the point counts wholes and the digit after the point counts tenths.
Worked examples
Write 7/10 as a decimal. The bar has 10 equal parts and 7 are shaded. 7/10 = 0.7, read seven tenths.
Write 0.4 as a fraction and find it on the number line. 0.4 = 4/10. Start at 0 and make 4 steps of one tenth.
What does 1.4 mean? It is 1 whole and 4 tenths: 1.4 = 1 + 4/10 = 1 4/10. The first bar is one whole, the second shows 4 tenths.
Class activity
Tenths in a ruler. Look at a ruler in centimetres. The distance between two numbers is divided into 10 millimetres. A length of 3 cm 7 mm is 3.7 cm. Measure three objects at home and write each length as a decimal in centimetres.
Practice
1
Write 9/10 as a decimal.
0.9, nine tenths.
2
Write 0.2 as a fraction.
2/10.
3
How many tenths make one whole? Write it as a fraction and a decimal.
10 tenths: 10/10 = 1.0 = 1.
4
Mina walked 6/10 of a kilometre. Write the distance as a decimal in kilometres.
0.6 km.
5
Aya writes 4/10 as 4.10. What is wrong? Write it correctly.
4.10 means 4 wholes and 10 hundredths. 4/10 is less than one whole, so it is 0.4.
