The analysis is as follows:

One round trip is equal to twice. He goes to and from school twice a day, 2*2=4 times, and each time he needs to walk 3 kilometers, 4*3 kilometers = 12 kilometers =1.2000 meters.

The calculation formula of distance is distance = time× speed, speed = distance/time, and time = distance/speed.

There are three situations involving the movement of two objects: opposite movement (encounter problem), same movement (chase problem) and opposite movement (separation problem).

But to sum up, whether it is the movement of one object or the movement of two objects, whether it is the opposite movement, the same movement or the opposite movement, their characteristics are the same. Specifically, they reflect the same quantitative relationship, which can be summarized as: distance = speed × time.

Extended data:

In science, speed is used to indicate the speed at which an object moves. Speed is numerically equal to the distance traveled per unit time. Calculation formula of speed: v = s/t The units of speed are m/s and km/h..

When the speed is constant to v', any distance is equal to the constant speed v' multiplied by the balance time t.

When the speed changes, although the equation does not hold, the proportional relationship will also go wrong, so the unbalanced nature of speed change and time change is not considered. Unbalanced attribute belongs to the relationship between unit and mode in its relativity, which can only be solved by constants.