SOLUTION: A tour bus leaves Sacramento every Friday evening at 5:00 P.M. for a 264-mile trip to Las Vegas. This week, however, the bus leaves at 5:15 P.M. To arrive in Las Vegas on time, the

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Question 915560: A tour bus leaves Sacramento every Friday evening at 5:00 P.M. for a 264-mile trip to Las Vegas. This week, however, the bus leaves at 5:15 P.M. To arrive in Las Vegas on time, the driver drives 8 miles per hour faster than usual. What is the bus's usual speed?
Answer by lwsshak3(11628) About Me  (Show Source):
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A tour bus leaves Sacramento every Friday evening at 5:00 P.M. for a 264-mile trip to Las Vegas. This week, however, the bus leaves at 5:15 P.M. To arrive in Las Vegas on time, the driver drives 8 miles per hour faster than usual. What is the bus's usual speed?
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let x=bus's usual speed
x+8=bus's faster speed
15 min=1/4 hr
travel time=distance/speed
..
264%2Fx-264%2F%28x%2B8%29=1%2F4
lcd:x(x+8)
264(x+8)-264x=x(x+8)/4
264x+2112-264x=(x^2+8x)/4
8448=x^2+8x
x^2+8x-8448=0
solve for x by quadratic formula:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a=1, b=8, c=-8448
ans:
x=-96 (reject)
or
x=88
bus's usual speed=88 mph