The hour hand walks a big grid, and the minute hand walks 60 small grids. * * * There are 12 big squares on the clock face, each big square is divided into 5 small squares, and * * * has 60 small squares. Clockwise 1 Yes 1 hour; Minute hand 1, minute hand 1 and minute hand 5. When the hour hand walks a big grid, then the minute hand walks a circle, and there are ***60 small grids. The elapsed time of the minute hand and the second hand can be converted to each other. Generally speaking, primary school mathematics will involve the related knowledge of clock time conversion. In the content of this lesson, students will have a deeper understanding of clocks, learn how to read the time displayed on clocks, and learn how to calculate the time difference between two time points. This knowledge is very useful to our daily life. Some pupils may have a headache about clocks, but don't worry too much. Generally speaking, they just need more practice to master them.

Clock watching method

1, there are 12 numbers on the clock, representing 12 hours. Each number represents an hour and also a minute, which is distinguished by the pointer.

The shorter hand on the clock is the hour hand, and the longer hand is the minute hand. What time does the hour hand indicate and what time does the minute hand indicate?

There are five cells between the two numbers, each cell represents one minute, and there are five minutes between the two numbers. One revolution of the minute hand is (1~ 12)60 minutes, which means that one revolution of the minute hand is 1 hour, and the hour hand just goes by a number, which is 1 hour. Now the clock refers to 12 hours and zero minutes, which is 65438.

Clock inventor

There are two theories about the invention of clocks and watches: the ancient Greeks and Zhang Heng of the Eastern Han Dynasty. From BC 140 to BC 100, the ancient Greeks made a timer for the Olympic Games, which consisted of 29 copper gears and several dials, and was called "Antikythera Instrument". From 78 AD to 139 AD in the Eastern Han Dynasty, Zhang Heng made a water leakage-turning armillary sphere, which combined the elephant with the timed leaky kettle through a gear system. The water dripping from the leaky kettle can push the elephant to rotate evenly once a day. This is the earliest mechanical clock.

Zhang heng

Zhang Heng is an outstanding inventor, astronomer, mathematician, geographer and writer. He has made outstanding contributions to astronomy and mechanical technology in China. His main works are Notes on Marriage View, Notes on Miraculousness, etc. It was honored as "Musheng" by later generations. Later, a mountain on the back of the moon was named "Zhangheng crater".