Answer: 4 hours, 36 minutes
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Step-by-step explanation:
x = number of hours spent going from college to home
9-x = number of hours spent going from home to college
Those two expressions add to 9 hours total.
Jenny travels for x hours at 66 mph. Her distance is 66x.
Recall that distance = rate*time, where "rate" is another term for "speed".
When returning back to college, she travels 9-x hours at 63 mph
Her distance is d = r*t = 63(9-x) = 567 - 63x
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When driving home, she travels 66x miles
When going back to college, she travels 567-63x miles
Assume she takes the same exact roads on either part of the round trip. If so, then those two distance expressions are equal.
Solve for x.
66x = 567 - 63x
66x + 63x = 567
129x = 567
x = 567/129
x = 4.3953488372093
x = 4.39535
That is the approximate number of hours spent going from the college to her home
So 9 - x = 9 - 4.39535 = 4.60465 is the approximate number of hours spent driving from her home going back to college.
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Let's rewrite that in hours,minutes format
We have 4 full hours plus an additional 0.60465 of an hour
Multiply this decimal by 60 to convert to minutes
60*0.60465 = 36.279
That rounds to about 36 minutes.
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The 4.60465 hours is about the same as 4 hours, 36 minutes when rounding to the nearest minute.