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, 2003

Algebra Difficulty 3.0 AMC 10/12 Prove it Canada

The assumption might be made that there are 24 times during any 12 hour period when the angle between the hour hand and the minute hand is $90°$ . This is not the case. Determine the actual number of times that the angle between the hour and minute hands is $90°$ .

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.