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Class trip savings — four classmates
Four classmates saved money for a class trip. Liam saved $15 less than Sara. Priya saved twice as much as Sara. Tom saved $9 less than Priya. Altogether the four classmates saved $126. How much did Tom save?
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The pattern behind it: Units and parts
Cut one amount into equal shares. One number tells you what a share is worth.
In this one. Complete Liam's and Tom's short bars by adding back $15 and $9; then all four amounts can be counted as six equal Sara-units.
How to spot it
A single amount is split by a ratio, a fraction or a percentage. One extra number gives you the leftover, the difference, or the value of one share.
Common mistake
Children match the given number to the wrong number of shares, using the whole bar when the number covers only the leftover or the difference between two people's shares.
Try one like it
Standard Concert tickets — four classes Four classes sold tickets to the school concert. Class 6B sold 10 fewer tickets than Class 6A. Class 6C sold twice as many tickets…The 33 problem patterns
All 33 patterns, one to a page — the 19 behind Primary 5 and 6 word problems, and the skills the younger years are built on. The bar model, how to spot it in the question, and the mistake children make. A booklet you can print. Free.
A PDF, and a note when new solutions go up.