Greg drove at a constant speed in a rainstorm for 245 245 miles. he took a break, and the rain stopped he then drove 160 160 miles at a speed that was 5 5 miles per hour faster than his previous speed. if he drove for 11 11 hours, find the car's speed for each part of the trip.

Question

Phoenix Kim

Physics

13 November, 03:35

Greg drove at a constant speed in a rainstorm for 245 245 miles. he took a break, and the rain stopped he then drove 160 160 miles at a speed that was 5 5 miles per hour faster than his previous speed. if he drove for 11 11 hours, find the car's speed for each part of the trip.

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Answers (1)

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Dario Curtis · Answer 1

distance = rate x time

245 = r * t

160 = (r+5) (11-t)

260 = 11r - rt + 55 - 5t

= 11r - 245 + 55 - 5t

160 = 11r - 190 - 5t

350 = 11r - 5t

rt = 245 - - - > t = 245/r

350 = 11r - 5 (245/r)

350 = 11r - 1225/r

350r = 11r^2 - 1225

0 = 11r^2 - 350r - 1225

0 = (11r + 35) (r-35)

11r + 35 = 0 results in negative rates and times

r-35 = 0 - - > r = 35.

He drove 35 mph for 245/35 = 7 hours in the rain.

He then drove 42 mph for 6 hours. That's 42 * 6 = 252 miles.