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Classical problems of mathematical rotation
2

35 minutes, 20 seconds /60 minutes =53/90

From 9: 00 to 10: 00, one * * *, five cars.

When the hour hand goes up at 9 o'clock, the square of 53/90*5=53/ 18 is between 47 and 48.

The minute hand is between 35 and 36 squares.

So a * * has 36 to 47 small lights. A * * 12。

1

A 90-degree meeting was held just after 7: 20.

A little after 7: 50, it was 90 degrees at one time.

Just after 8: 25, it was 90 degrees.

There is a period of time between topics.

It means a little after 7: 20.

The end time is a little over 8: 25.

Divide the clock into 60 units.

At 90 degrees, this means that it is only 15 square short.

Let 7: 20+x minutes be 90 degrees.

The minute hand walks 60 squares and the hour hand walks 5 squares.

112 means that the hour hand is the minute hand.

(20+x)/ 12+35 = 20+x+ 15

35 is the position of 7 o'clock, and 15 is 90 degrees apart.

12x=20+x

X=20/ 1 1 approximately = 1.8.

So the story starts at 7 o'clock, 2 1.8, which means 7 o'clock, 2 1: 49.

Calculate the end time in the same way.

(25+x)/ 12+40 = 25+x+ 15

X=25/ 1 1 approximately =2.27.

That was at 8: 27: 27, that is, 8: 27, 16 seconds.