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Ten Green Bottles
Ten green bottles hanging on a wall
Ten green bottles hanging on a wall
If one green bottle should accidentally fall
There'd be nine green bottles hanging on the wall
Nine green bottles .....


If the first bottle fell at ten past five in the morning ($5.10$ a.m.) and the others fell down at $5$ minute intervals, what would the time be when the last bottle fell down? 
Why do this problem?
This problem is one which could be done quickly as an introduction when extending or revising work on time and clocks.
Key questions
When does the first bottle fall?
So when does the second bottle fall?
How many $5$ minutes are there between the first and tenth bottles falling?
Possible extension
Learners could find the equation for the $nth$ bottle falling.
Possible support
Suggest using a real or model clock and counting.