SOLUTION: a man made a trip of 275 miles in 8 hours. before noon, he averaged 40mph , and after noon he averaged 25 pmh. at what time did he begin his trip ?

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Question 251115: a man made a trip of 275 miles in 8 hours. before noon, he averaged 40mph , and after noon he averaged 25 pmh. at what time did he begin his trip ?
Found 2 solutions by solver91311, checkley77:
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


Distance equals rate times time.

The distance he traveled before noon is equal to 40 mph times the time he traveled before noon, so:



The distance he traveled after noon is equal to the entire trip minus the distance he traveled before noon AND is equal to 25 mph times the time he traveled after noon which is equal to 8 hours minus the time he traveled before noon, so:



Since the first expression gives us an expression in that is equal to , we can make a convenient substitution:



Now all you need to do is solve for which will be the number of hours traveled before noon. Subtract from 12 noon to find the time he started in the morning.

John

Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
D=RT
275=40X+30(8-X)
275=40X+240-30X
10X=275-240
10X=35
X=35/10
X=3.5 HOURS FOR THE 40 MPH TRIP.
8-3.5=4.5 HOURS FOR THE 30 MPH TRIP.
12:00-3:30=8:30 IS THE TIME OF THE BEGINNING OF HIS TRIP.