Tina is training for a biathlon. To train for the running portion of the race, she runs 14 miles each day, over the same course. The first 4 miles of the course is on level ground, while the last 10 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) 12 mph
B) 15 mph
C) 18 mph
D) 30 mph
E) 9 mph

Question

Quizplus · Accepted Answer

Let's call Tina's speed on downhill terrain "x". Then her speed on level ground will be "x-3" since she runs 3 mph slower. We can set up an equation based on the given information:
4/(x-3) + 10/x = 1
Solving for x, we get x = 15 mph. Therefore, Tina's speed on the downhill part of the course is 15 mph. So the answer is B (15 mph).

Tina Is Training for a Biathlon