SOLUTION: Tina is training for a biathlon. To train for the running portion of the race, she runs 10 miles each day, over the same course. The first 4 miles of the course is on level ground,

Question 887211: Tina is training for a biathlon. To train for the running portion of the race, she runs 10 miles each day, over the same course. The first 4 miles of the course is on level ground, while the last 6 miles is downhill. She runs 4 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?
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
Tina is training for a biathlon. To train for the running portion of the race, she runs 10 miles each day, over the same course. The first 4 miles of the course is on level ground, while the last 6 miles is downhill. She runs 4 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?
***
let x=speed Tina runs downhill
x-4=speed Tina runs on level ground
travel time=distance/speed

lcd:x(x-4)
6x-24+4x=x^2-4x
x^2-14x+24=0
(x-12)(x-2)=0
x=2 (reject)
or
x=12
x-4=8
speed Tina runs downhill=12 mph
speed Tina runs on level ground=8 mph
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