Question 253161: 1.)two airplanes take off at Manila Domestic Airport at the same time and fly in opposite directions. Their rates are 840kph and 860kph. Find the elapsed time when thy are 6800 km apart?
2.)Two men start from different points and travel towards each other. The rate of the first man is 5.6kph and tht other travels 0.4kph fatster than the first. How far apart were they after 1.5hours?
3.)A starts from the starting line and runs at a rate of 12kph. B leaves the starting line 12min later and runs at 18kph. In how many hours will B overtake A?
4.)A farmer with his fully loaded produce truck travels to market at 60kph. He leaves at 6am. The return trip begins at 3pm travelling at 80kph ang takes 1.5hours less time. Find the total travel time for the trip to and from the market.
Answer by Greenfinch(383)   (Show Source):
You can put this solution on YOUR website!
1 . Forget the airport. Planes are moving apart at 840 + 860 = 1700 kph
Time when 6800 apart is 6800/1700 = 4 hours
2. 1st man does 5.6 kph, second man does 6 kph, total closing velocity is 11.6 kph. After 1.5 hours they are 1.5 x 11.6 = 17.4 km closer that at the start
3. after 12 minutes, a has a lead of 12/5 = 2.4 km (12 minutes = 1/5 of hour)
difference in velocity between A and B is 6 kph, so how long does it take to cover 2.4 km at 6 kph. (2.4 / 6) = 2.5 hour or 24 minutes.
4. The time he leaves is irrelevant.
Distance = 60T = 80 (T - 3/2)
60T = 80T - 120
so T = 6
Total time is therefore 6 + 4.5 = 10.5 hours
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