3
Review: sums, time and graphs
Discover Mathematics: Chapters 1–7
GoalAdd and take away within 20, tell the time to the hour, and read a picture graph.
New words
add · put groups togethertake away · some go away, count what is lefto’clock · exactly on the hourgraph · a picture that shows counts
Explanation
To add, we put groups together and count them all. If the total goes past ten, fill a ten-frame first. To take away, we cross out what goes and count what is left. To tell the time, look at the short hand for the hour. When the long hand points to 12, it is an o’clock time. In a picture graph, the longest row is the one most children chose.
Worked examples
9 + 5 = 14. Move 1 dot to fill the first ten-frame to 10, and 4 more are left.
Rahma has 12 balloons. 4 fly away. 12 − 4 = 8, so 8 are left.
In the graph, 4 children chose tea and 6 chose juice. Juice has the longest row, so most children chose juice.
Class activity
Shop and clock. Set up a pretend shop with 10 to 15 small things. Let the child add two piles and take some away, saying the sums aloud. Then ask what o’clock the shop opens and closes, and show it on a paper clock.
Practice
1
Add: 9 + 4. Look at the ten-frames.
13
2
What is 15 − 6? Count what is not crossed out.
9
3
What time does the clock show?
1 o’clock
4
In the graph, how many children chose green?
3
5
The family is 5, 7 and 12. Write the answer: 12 − 5 = __.
7