1. If facing east, the back is west, the left is north, and the right is south. If facing west, the back is east, the left is south and the right is north. If you face south, your back is north, your left is east and your right is west.

2, 1 = 60 minutes, 1 minute = 60 seconds.

3. Elapsed time = end time-start time; Start time = end time-elapsed time; End time = start time+elapsed time.

There are 12 big squares and 60 small squares on the clock. It takes 1 hour to walk a big square in an hour hand, 1 minute to walk a Little Square in a minute hand and 5 minutes to walk a big square in a minute hand.

5. According to the relationship between the parts of division, several formulas can be derived: dividend = divisor × quotient+remainder; Divider = (dividend-remainder) ÷ quotient; Quotient = (dividend-remainder) divider; Remainder = dividend divided by quotient.

6. In the formula without brackets, there are addition, subtraction, multiplication and division. Multiply and divide first, then add and subtract. If there is only addition and subtraction or only multiplication and division, it should be calculated from left to right. Formulas in brackets should be calculated first.