3
Review: data and mixed problems
Discover Mathematics P2: Term 2, Lessons 61–120
GoalReview reading bar graphs and pictographs, and solve mixed story problems.
New words
bar graph · bars show numbers; a taller bar is a bigger numberpictograph · pictures show numbers; read the key firstcompare · find how many more or fewer
Explanation
To read a bar graph, look at the top of each bar and find its number. The tallest bar is the most and the shortest bar is the least. Add the bars to find the total, and subtract to compare. For a pictograph, read the key first. If one picture is 2, then 6 pictures are 2 + 2 + 2 + 2 + 2 + 2 = 12. In story problems decide: put together means add, left means take away, how many more means compare.
Worked examples
The graph shows favourite colours. Blue has the tallest bar: 9 children. Yellow has the shortest bar: 4 children.
In this pictograph one fish is 2 fish. Pond A has 5 pictures, which is 10 fish. Pond B has 3 pictures, which is 6 fish. 10 − 6 = 4 more fish in pond A.
A class has 28 children. 13 are girls. How many are boys? Part and whole: 28 − 13 = 15 boys.
Class activity
Make a class graph. Ask ten people their favourite colour: red, blue, green or yellow. Make tally marks, then draw a bar graph with a title. Write two questions about your graph, one about the most and one about how many more, and let someone answer them.
Practice
1
How many children chose blue?
9 children.
2
How many more children chose blue than yellow?
9 − 4 = 5 more children.
3
How many children are in the graph in all?
5 + 9 + 6 + 4 = 24 children.
4
In a pictograph one picture is 2. There are 6 pictures. How many does that show?
2 + 2 + 2 + 2 + 2 + 2 = 12.
5
A shop has 340 eggs and gets 160 more. How many eggs does it have in all?
340 + 160 = 500 eggs.