GoalMake a bar graph from a table and read facts from it.
New words
bar graph · a graph that uses bars to show datatitle · the name of the graph; it says what the graph is aboutaxis label · words that tell what each side of the graph showsscale · the numbers along the side, counted in equal steps
Explanation
A bar graph turns a table into a picture. Step 1: write a title that says what the graph is about. Step 2: label both axes, for example Child along the bottom and Number of brothers and sisters up the side. Step 3: choose a scale that is high enough for the biggest number and counts in equal steps. Step 4: draw one bar for every row of the table, all with the same width, and colour them. To read a graph, find the top of a bar and follow it across to the scale. The tallest bar is the most and the shortest bar is the least.
Worked examples
Child
Brothers and sisters
Youssef
2
Salma
3
Omar
1
Farida
4
Karim
2
This table shows how many brothers and sisters five children have. Each row becomes one bar: Youssef 2, Salma 3, Omar 1, Farida 4 and Karim 2. The tallest bar will be Farida's, and the scale only needs to reach 4. In all they have 2 + 3 + 1 + 4 + 2 = 12 brothers and sisters.
Uncle Hassan sells boxes of sweets. The graph shows five days. The tallest bar is Saturday with 14 boxes and the shortest is Monday with 6 boxes. Saturday sold 14 − 6 = 8 more boxes than Monday. In all he sold 14 + 10 + 6 + 8 + 12 = 50 boxes.
Forty children chose a favourite fruit. The scale counts in 5s, so each bar ends exactly on a line, and the number on top of each bar helps. 15 + 10 + 5 + 10 = 40, so every child is in the graph.
Class activity
Class survey. Ask 10 people which colour they like best: red, blue, green or yellow. Make a tally, then draw a bar graph on squared paper with a title, labels on both sides and a coloured bar for each colour. Write two questions that a friend can answer by looking at your graph.
Practice
1
Who read the most books?
Nour read the most: 6 books.
2
How many books did the four children read in all?
3 + 6 + 4 + 5 = 18 books.
3
Name three things that every bar graph needs.
A title, labels on both axes and a scale with equal steps. Bars of the same width are also needed.
4
Jana will draw a bar graph from this table. How tall is the cat bar? How many more cats than birds are there?
Pet
Number
Cats
7
Birds
3
Fish
5
The cat bar goes up to 7. There are 7 − 3 = 4 more cats than birds.
5
A graph shows trees planted: Sunday 12, Monday 8, Tuesday 9 and Wednesday 6. Which day has the shortest bar? How many trees in all?
