Question

Jan walks 2 miles at a constant rate of 3 miles per hour and then runs 1 mile at a constant rate of 8 miles per hour.

(a) What is Jan’s average speed for the entire trip?
(b) Is the average speed in part (a) equal to the average of Jan’s two speeds?

Answer 1

(a).4.36 mph

(b) No

Explanation:

We are given that

Jan covered distance,s1 =2 miles

Speed of Jan, a=3 mph

s2=1 mile

b=8mph

a.

We have to find the Jan' s average speed for the entire trip.

Average speed =
`(2ab)/(a+b)`

Using the formula

Average speed=
`(2(3)(8))/(3+8)=4.36mph`

b.

Average speed with two speed

Average of Jan’s two speeds

`=(a+b)/(2)`

=
`(3+8)/(2)=5.5 mph`

`4.36\\eq 5.5`

Hence, the average speed in part (a) is not equal to the average of Jan’s two speeds.