alleryA 100 km trip takes one hour less when speed rises from x to x+5 km/h. Find x.
A15 km/h
B20 km/h
C25 km/h
D30 km/h
Answer & Solution
Correct answer: B. 20 km/h
100/x−100/(x+5)=1 reduces to x²+5x−500=0, whose positive root is 20.
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