Speedboats — the Dolphin and the Marlin race to an island
Two speedboats, the Dolphin and the Marlin, raced from the same jetty to an island. Both left at 08:00 and did not change their speed throughout the journey. The Dolphin travelled at a constant speed of 40 km/h. When it reached the island at 08:30, the Marlin was 2 km from the island. What was the Marlin'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. Compare both boats at the same 08:30 snapshot: because they have travelled for the same time along the same route, subtracting Marlin's remaining gap from Dolphin's full route gives Marlin's distance directly.
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
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