1
Our class graph
Discover Mathematics P2: Term 1, Lessons 2–10
GoalCollect votes with tally marks and show them in a bar graph with a title.
New words
data · facts we collect, like the answers of childrentally mark · one small line for each answerbar graph · a picture that uses bars to show how manytitle · the name that tells what the graph is about
Explanation
To learn what a group likes, we ask each child and keep the answers. These answers are called data. For every answer we make one tally mark. The fifth mark goes across the four before it, so we can count in fives. Then we draw one bar for each choice. The taller the bar, the more children chose it. Do not forget a title, such as Our favourite fruit.
Worked examples
Mina asked 9 friends which fruit they like best. She got banana 4, orange 3 and apple 2. She draws one bar for each fruit: 4 squares, 3 squares and 2 squares tall.
Seven votes are drawn as one group of five (four lines and a line across them) and two more lines.
In Mina’s graph the banana bar is the tallest, so most children like bananas. The apple bar is the shortest. Banana has 4 − 2 = 2 more votes than apple.
Class activity
Vote at home. Ask each person in the family: Which fruit do you like best? Make a tally mark for each answer. Then draw the graph on squared paper, one square for each vote, and write a title above it.
Practice
1
How many votes do these tally marks show?
8 (one group of five and 3 more)
2
Hana asked her class about sports: football 5, swimming 3, tennis 2. How many children voted in all?
10
3
In Hana’s tally, how many more children chose football than tennis?
3
4
Karim wants to draw a graph of these sport votes. Give it a good title.
Any good title, for example Our favourite sport.
5
Draw 6 votes as tally marks. How many lines are across the others?
One. Four lines, one line across them, and one more line.