Digits, Grade 7, Volume 1, Homework Helper

## Topic 7: Proportional Relationships

### 7-1: Constant Speed

#### Key Concept

The equation d = rt expresses the relationship between distance d, speed r, and time t.

Constant Speed Constant speed is a rate comparing distance to time. If the car travels 10 miles in 1 hour, the car's speed is the rate 10 . fraction miles , over hour end fraction . .

Time The total distance the car travels depends on the total amount of time. The speed of the car is given in miles per hour, so the number line shows the time in hours.

Distance For each hour the car travels, the total distance increases by 10 miles.

Using d = rt You can use the equation d = rt to find a distance, rate, or time. The diagram above shows two distances, the first after 1 hour and another after 6 hours.

#### Part 1

Example Finding Distances Driven For Fixed Time at Constant Speeds

Your aunt drives at a constant speed of 45 miles per hour. How far will your aunt travel in 20 minutes? Use the equation d = rt, where d is distance, r is rate, and t is time.

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