SOLUTION: Christine and Jessica leave from the same spot at the same time and begin jogging in opposite directions. At the end of an 1 1/2 hours they are 15 miles apart. Find Christine's av

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Question 369512: Christine and Jessica leave from the same spot at the same time and begin jogging in opposite directions. At the end of an 1 1/2 hours they are 15 miles apart. Find Christine's average speed if her average speed is 2 miles per hour more than Jessica's average speed.
Answer by CharlesG2(834) About Me  (Show Source):
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Christine and Jessica leave from the same spot at the same time and begin jogging in opposite directions. At the end of an 1 1/2 hours they are 15 miles apart. Find Christine's average speed if her average speed is 2 miles per hour more than Jessica's average speed.

distance D = rate R * time T
let R = Jessica's average speed
let R + 2 = Christine's average speed
let T = 1 1/2 = 1.5 hours
let D = total distance of 15 miles
15 = R * 1.5 + (R + 2)1.5
15 = 1.5R + 1.5R + 3
12 = 3R
4 = R
Jessica's average speed is 4 mph
Christine's average speed is 6 mph
Jessica's distance = 4 * 1.5 = 6 miles
Christine's distance = 6 * 1.5 = 9 miles
6 miles + 9 miles = 15 miles