Question

Jenn drove 35 miles in half the time it took Brian to drive 35 miles. If Jenn's average speed was r miles per hour, what was Brian's average speed, in mph?

A.) 3r
B.) r
C.) r/2
D.) r+2

Answer 1

Brian's average speed is r/2 since Jenn drove the same distance in half the time with an average speed of r. To find Brian's average speed, use the average speed formula with the time doubled compared to Jenn's time. option c is correct.

Step-by-step explanation:

Jenn's scenario can be represented by calculating average speed in terms of distance and time. Since Jenn and Brian both drove 35 miles but Jenn did so in half the time, we can set up an equation using average speed = distance / time.

Let t be the time it took Brian to drive 35 miles. Jenn then took t/2 to drive the same distance.

Jenn's average speed is given by r, so:

r = 35 miles / (t/2) hours

Therefore, t = (35 miles) / r * 2

To find Brian's average speed, we use the formula:

Brian's average speed = 35 miles / t

Plugging in the value of t we got from Jenn's time, we have:

Brian's average speed = 35 miles / (2 * 35 miles / r)

Simplifying this, we get:

Brian's average speed = r/2

So, the correct answer is C.) r/2.