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Ten Green Bottles

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Take the Right Angle

Stage: 2 Challenge Level: Challenge Level:1

Abby, Antony, James and Peter from Gateway school in Carterton wrote to say:

We found 22 right angles in 12 hours. All the right angles are listed below:
12:16 12:49 1:22 1:54 2:27 3:00 3:33 4:05 4:39 5:11 5:44 6:16 6:49 7:22 7:54 8:27 9:00 9:33 10:05 10:39 11:11 11:44.

One of these is a minute out according to the NRICH clock. Can you find which one?

William and Alex at Maadi British International School, Cairo used a wrist watch to work out the problem and agreed there were 22 right angles, so did Eliza and Milli from St Hilda's School.