The time needed for a 15 miles long hike depends on the average speed of the hiker. Write the formula that describes this time as the function of the average speed.
Question
Answer:
t(r) = 15/rWe start out with the formula for distance, d = rt, where d is the distance, r is the rate (speed), and t is the time. We know the distance is 15 miles:
15 = rt
We want this as a function of the speed; this means we want speed to be the independent variable and time to be the dependent. We cancel the r away from t by dividing:
15/r = rt/r
15/r = t
Now we write it in function notation:
t(r) = 15/r
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