Discover Mathematics P5: Term 1, Unit 5, Lessons 11–14
GoalUse tenth and hundredth models to divide a decimal by a whole number and to see how many small decimals fit in a bigger one.
New words
share equally · to split an amount into groups of the same sizeregroup · to trade one place for ten of the next smaller place, such as 1 tenth for 10 hundredthsquotient · the answer to a division
Explanation
A model turns a decimal division into a whole-number division. 1.2 is 12 tenths. Share 12 tenths among 4 equal groups and each group gets 3 tenths, so 1.2 ÷ 4 = 0.3. If the tenths do not share evenly, regroup: 0.4 is 4 tenths, which is the same as 40 hundredths. Sharing 40 hundredths among 5 gives 8 hundredths, so 0.4 ÷ 5 = 0.08. Division also asks “how many fit?”. To find how many 0.2 fit in 1.4, count in tenths: 14 tenths ÷ 2 tenths = 7. In both cases name the unit (tenths or hundredths), divide the counts, and give the answer in the same unit.
Worked examples
Share 1.2 kg of dates equally among 4 baskets. 1.2 kg = 12 tenths of a kg. 12 ÷ 4 = 3, so each basket gets 3 tenths: 0.3 kg. Check: 4 × 0.3 = 1.2.
Start
In hundredths
÷ 5
Answer
0.4
40
8
0.08
Work out 0.4 ÷ 5. Four tenths cannot be shared among 5 with whole tenths, so regroup: 4 tenths = 40 hundredths. 40 ÷ 5 = 8 hundredths. So 0.4 ÷ 5 = 0.08.
How many glasses of 0.2 L can be filled from a 1.4 L jug? 1.4 L = 14 tenths and 0.2 L = 2 tenths. 14 ÷ 2 = 7, so 7 glasses.
Class activity
Paper strips. Take a long paper strip as 1 whole. Fold it into 10 equal parts and colour 6 of them: that is 0.6. Share the coloured part among 3 friends and say how many tenths each gets. Then colour 4 tenths, fold each tenth into 10 equal parts, and share the 40 small parts among 5 friends. What does each friend get?
