This is the third topic the the Math Word Problems Solving Series. In this series, we are going to learn about motion problems — problems about distance, rate, and time.

In motion problems, a car traveling 70 kilometers per hour is mostly assumed to be traveling at a constant speed. Of course, this is not true in the real world. In reality, we can think of 70 kilometers per hour as the average speed of the car.

If we want to find the distance traveled by a car traveling at 70 kilometers per hour in 3 hours, it is clear that we have to multiply the *rate* and the *time*. The rate of the car is 70 kilometers per hour and the time elapsed is 3 hours. So,

distance traveled = (70 km/hr)(3 hrs) = 210 km.

In general, the distance traveled by a moving object at a rate * *having an elapsed time * *is described by the equation

.

Most motion problems that we will discuss are about two traveling objects with different speeds. The objects can be traveling away or towardea ch other. Take note of the formula above because we are going to use it in almost all the problems that will be discussed later in this series.

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*Photo Credit (Creative Commons): Amalakar via Flickr*

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