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Math problems in the fifth grade of primary school:
Analysis: the speed of the minute hand is 16 times that of the hour hand, the speed of the second hand is 36 times that of the hour hand, the instant hand goes 1, the minute hand goes 16, and the second hand goes 36 times. The speed difference between the minute hand and the hour hand is: 16- 1 = 15, and the time for the minute hand to catch up with the hour hand for the first time is: 360 ÷ 15 = 24 (the unit time of the hour hand) (the instantaneous hand goes 1).

The speed difference between the second hand and the hour hand is 36- 1 = 35. The time for the second hand to catch up with the hour hand for the first time is: 360 ÷ 35 = 10 2/7 (unit time). When catching up for the first time, go clockwise 1 × 66.

A * * * can catch up with (overlap) 360÷ 10 and 2/7 = 10 (times).

Three-stitch overlap, that is, the least common multiple of 24 and 10 2/7 is 72, which is the first three-stitch overlap, and then it will overlap every 72 stitches. In a circle, a * * * overlap: 360 ÷ 72 = 5 times, regardless of the starting point and ending point, it must be subtracted once.