, 24 November 2021
Difficulty: Fun
The number 39 bus was packed as it pulled into the interchange. Then 37 people got off, and another 14 got on. As the bus left the interchange, there were 37 people on board.
How many people were on the bus as it pulled into the interchange?
Scroll down or click for a hint, or the answer!
Start with 37 people on the bus and work backwards in time! Remember to add the people getting off, and subtract the people getting on – everything is backwards.
To solve this brainteaser, we’re going to work backwards in time.
When the bus left there were 37 people on board. Just before the bus left, 14 people got on. Before they did, there must have been 37 – 14 = 23 people on the bus.
Before those people got on the bus, 37 people got off. So initially there must have been 23 + 37 = 60 people on the bus.
60 people is the answer! To check, we can run the story forwards.
60 – 37 + 14 = 37
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