MathJewels math guide · Interpret a scaled picture graph
Reading a Scaled Picture Graph
Use the graph key as a multiplication rule: each picture may represent several objects rather than just one.
The big idea
In a scaled picture graph, a picture is a unit with a value. The key might say that one cart stands for 4 loads or one star stands for 5 votes. Counting pictures is only the first step. Multiply the number of pictures by the value of each picture to recover the actual quantity.
Read the key before reading any row. The same symbol must keep the same value throughout the graph.
Worked example
A key says 1 gem picture = 3 gems. The ruby row contains 4 pictures. The row represents 4 × 3 = 12 rubies. If the sapphire row contains 2 pictures, it represents 6 sapphires, so the ruby row has 12 − 6 = 6 more gems.
How children may show it
A child may write the value under each picture, skip-count by the key value, or write one multiplication equation for each row. When comparing categories, it helps to write both actual totals before finding a difference.
Common mix-up
A frequent error is reporting 4 because there are 4 pictures, even though each picture represents 3. Point to the key and ask, “What amount is hidden inside every picture?” Also check partial pictures carefully; they represent the same fraction of the key value.
Try it together
Draw three simple symbols and choose a key such as 1 symbol = 2. Ask the child to name the represented total. Then reverse the task: request a total of 8 and ask how many symbols the graph needs. Reversing the question checks that the key is understood as a relationship.