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Race cars — Car A and Car B
Two remote-control race cars, Car A and Car B, started from the same line on a track at 14:00. Both did not change their speed throughout the race. Car A travelled at a constant speed of 36 km/h. When it crossed the finish line at 14:20, Car B was 1.5 km from the finish line. What was Car B's speed?
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The pattern behind it: Same time, same distance
Two travellers spend the same time, or cover the same distance.
In this one. Because both cars raced for the same 1/3 h on the same track, Car B's distance is the full track length minus its remaining gap.
How to spot it
Two travellers set off together or one chases another, with constant speeds and a question about who is ahead, when they meet, or how far apart they are.
Common mistake
Children divide the whole distance by the difference in speed instead of dividing the gap between the travellers, or compare distances covered over different lengths of time.
Try one like it
Standard Aladdin and Jasmine — the magic carpet race Aladdin and Jasmine were having a race on their magic flying carpets. They left the same starting point for the market at 13 00. B…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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