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jmc

prealgebra senior

Problem

At what is the degree measure of the smaller angle formed by the hour and minute hands of a -hour clock?
Solution
We consider a hand at the 12 to be . Now we convert the hour and minute hands to a degree measure from to . If we divide evenly among 60 minutes, we get that each minute, the minute hand moves . So if the minute hand is at 48 minutes, it is at .

The hour hand is a little trickier. If we divide evenly among 12 hours, we get that each hour, the hour hand moves . Note that the hour hand is not at the 2 since it gradually moves toward the 3 throughout the hour. From the 2 toward the 3, the hour hand has moved of the way. So the degree measure of the hour hand is .

To find the smaller angle formed by the two hands, we can find the larger angle and subtract from to get . Or we know that is coterminal with (ends at the same place as) . Now we can subtract to find the smaller angle.
Final answer
156^\circ