Picture graphs with a scale

Read the key first

A class records books read. One dot stands for two books.

Group A has three symbols, but it read six books: 3 × 2 = 6. Group B read ten books. Group C read four books.

The key changes what a symbol means. Do not count three symbols and report three books.

Compare totals in the question’s unit

Group B read four more books than Group A: 10-6 = 4. You can also see two extra dots, with two books in each: 2 × 2 = 4.

Groups A and C together read 6 + 4 = 10 books. There are five dots across those two rows, and 5 × 2 = 10 checks the total.

Check your understanding 1 Combine all the groups

How many books did Groups A, B and C read altogether?

Total books

Check answer

Show answer

20 books: 6 + 10 + 4 = 20. Counting ten dots without applying the key gives the number of symbols, not the number of books.

A different key makes a different graph

If one symbol stands for five pupils, four symbols stand for 20 pupils. If each symbol stands for ten pupils instead, the same four symbols stand for 40 pupils. The symbols alone do not tell you the total.

A half-symbol, when the key permits it, represents half the value of a full symbol. With one symbol for two books, a half-symbol represents one book. Check the key and what the graph actually shows before using this.

Check your understanding 2 Choose a matching row

A new graph uses one star for five stickers. Jo has 15 stickers and Sam has 25. How many stars should each row have? How many more stickers does Sam have?

Your answer or drawing on paper

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Jo needs 15÷5 = 3 stars and Sam needs 25÷5 = 5 stars. Sam has 25-15 = 10 more stickers. The two extra stars each stand for five stickers, so they also show a difference of ten.

Decide what is known

The first graph counts books for three groups. It does not tell you how long each group read or whether every book had the same number of pages. Use the graph for the quantities it records, rather than guessing a reason for the differences.