Tina is training for a biathlon. To train for the running portion of the race, she runs 8 miles each day, over the same course. The first 2 miles of the course is on level ground, while the last 6 miles is downhill. She runs 3 miles per hour slower on level ground than she runs downhill. If the complete course takes 1 hour, how fast does she run on the downhill part of the course?
A)6 mph
B)9 mph
C)18 mph
D)3 mph
E)12 mph

Question

Quizplus · Accepted Answer

Let x be the speed at which Tina runs downhill. Then her speed on level ground is x - 3. 
Using the formula distance = rate × time, we can set up the equation:
2(x - 3) + 6x = 8 
Simplifying the equation: 
2x - 6 + 6x = 8 
8x = 14 
x = 1.75 
Therefore, Tina runs downhill at a speed of 1.75 + 3 = 4.75 mph. Rounded to the nearest whole number, this is 5 mph. So, the best choice is B.

Tina Is Training for a Biathlon