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Two tanks — same flow rate, equal height
Two rectangular tanks are shown below. At first, Tank A was empty and one third of Tank B was filled with water. Both taps were turned on at the same time and water from both taps flowed at the same rate of 1.2 litres per minute. How long did it take for the height of the water to be the same in both tanks?
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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. The same volume per minute poured into a smaller base area makes a faster rise, so the height gap between the two tanks shrinks at a fixed number of centimetres each minute — find the gap, find the rate it closes at, and divide.
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.
A PDF, and a note when new solutions go up.