SOLUTION: Car A is traveling along a freeway at 100km/h when it is passed by car B. If both cars maintain a constant speed and the end of the freeway is in 10km away, find the speed at which

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Question 1110487: Car A is traveling along a freeway at 100km/h when it is passed by car B. If both cars maintain a constant speed and the end of the freeway is in 10km away, find the speed at which car B must travel to beat car A to the end of the freeway by one minute.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+100+ km/hr = speed of car A
Let +100+%2B+s+ = speed of car B
Convert minutes to hrs
+1%2A%281%2F60%29+=+1%2F60+ hrs
Let +t+ = time in hrs for car A to
travel +10+ km
------------------------------
Car A's equation:
(1) +10+=+100t+
Car B's equation:
(2) +10+=+%28+100+%2B+s+%29%2A%28+t+-+1%2F60+%29+
-------------------------------------
(1) +t+=+1%2F10+
Plug (1) into (2)
(2) +10+=+%28+100+%2B+s+%29%2A%28+6%2F60+-+1%2F60+%29+
(2) +10+=+%28+100+%2B+s+%29%2A%28+1%2F12+%29+
(2) +100+%2B+s+=+120+
(2) +s+=+20+ km/hr
-------------------------------------
Car B's speed is +100+%2B+s+=+120+
120 km/hr
-------------------------------------
check:
(2) +10+=+%28+100+%2B+20+%29%2A%28++t+-+1%2F60+%29+
(2) +10%2F120+=+t+-+1%2F60+
(2) +t+=+5%2F60+%2B+1%2F60+
(2) +t+=+6%2F60+
(2) +t+=+1%2F10+
OK