Question

Joe began to increase the speed of his car at 2:00 P.M. Since that time,the speed of Joes car has been steadily increasing by 1 1/2 miles per hour for each half minute that has passed. If the car is now traveling 65 1/2 miles per hour, for how many minutes has the car been exceeding the speed limit for 55 miles per hour?
A. 3 1/3 min
B. 3 1/2 min
C. 4 1/2 min
D. 5 min
E. 7 min

Answer 1

Answer:

7 mins

Step-by-step explanation:

Current speed of Joes Car = 65.5 mph

We have to find the time interval for which the car exceeded the speed limit of 55 mph.

While, we are given that the speed of the car was constantly increasing, hence the speed over all increased from the limit of 55 mph = 65.50-55.00 = 10.50 mph

We are also given that Joes car was increasing speed at a constant rate of 1.50 mph for every passing minute. Hence

1.50 mph is increased in 1 minute

1 mph will be increase in $\frac{1}{1.5}$ minutes

Hence

10.50 mph will be increased in $\frac{1}{1.5} \times 10.50$ minutes

$= \frac{10.5}{1.5}$

$=7$

Hence joes car was exceeding the limit of 55 mph for 7 minutes.