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810 workers — who finished on time
A factory has 810 workers, made up of assembly-line workers and packing workers. of the assembly-line workers and of the packing workers finished their shift on time. The number of assembly-line workers who did not finish on time is three times the number of packing workers who did not finish on time. How many packing workers did not finish on time?
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The pattern behind it: The equal concept
The question tells you a part of one pile equals a part of another.
In this one. Scale 1/3 to 5/15; when both late amounts are shown as the same five equal parts, compare the 12-part and 15-part wholes to get the group ratio.
How to spot it
Two different groups each get their own fraction or percentage, and the question links them with 'the same as', 'twice as many as', or a shared cost across different units.
Common mistake
Children compare the two fractions without first relating them to a common whole. A smaller fraction of a larger group can be bigger than a larger fraction of a smaller group.
Try one like it
Challenging 370 visitors — who bought a raffle ticket A charity fun fair had 370 visitors, made up of children and adults. 7/9 of the children and 7/10 of the adults bought a raffle ti…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.
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