Thursday, November 19, 2009

The Clock Puzzle

The Problem: If you look at a clock and the time is 4:20, what is the angle in degrees between the hour and the minute hands? (The answer to this is not zero!)

The Answer: 10 degrees. First, some basic math: every minute on the clock is 6 degrees (360 degrees divided by 60 minutes = 6 degrees per minute). Although the minute hand is directly on the "4" on the face of the clock, the hour hand no longer is. Why? The hour hand was directly on the "4" at 4:00, but at 4:20 it's already a third of the way into its journey from the "4" to the "5." Every hour, the hour hand moves 30 degrees (five minutes). Since it is exactly 1/3 past the hour, the hour hand is 1/3 of the way into its 30-degree trip, which is 10 degrees past the "4" on the face.

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