SOLUTION: On a 5 hr trip thomas drove part of the time at 30mph and the rest 55 mph. if he traveled a distance of 250 miles, how much time did he spend driving at 55mph?

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Question 117573: On a 5 hr trip thomas drove part of the time at 30mph and the rest 55 mph. if he traveled a distance of 250 miles, how much time did he spend driving at 55mph?
Answer by solver91311(24713) About Me  (Show Source):
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The standard formula for straight line trips is d=rt.

He traveled some distance d%5B55%5D at 55 mph for some time t and he travelled some distance d%5B30%5D at 30 mph for the rest of the 5 hours, or 5-t. These two distances add up to 250 miles.

d%5B55%5D=55t, and
d%5B30%5D=30%285-t%29, and
d%5B55%5D%2Bd%5B30%5D=250

55t%2B30%285-t%29=250
55t-30t%2B150=250
25t=100
t=4
So he travelled for 4 hours at 55 mph, and 1 hour (5 - 4) at 30 mph
Check the answer:
d%5B55%5D=55%284%29=220
d%5B30%5D=30%281%29=30, and
220%2B30=250, check.