In a bicycle race Lional gives Robert a 500m advantage Also

In a bicycle race, Lional gives Robert a 500m advantage. Also, Lional agrees to start 15 minutes after Robert. If Lional bikes at 17km/hr and Robert at 14km/hr, how long will it take Lional after he starts biking to overtake Robert?

Solution

Answer: 2 hours and 50 minutes.
Robert is 500 meters ahead.
Then for the next 15 minutes Robert travels 14 km/hour (1400 meters/hour)
15 minutes is 1/4 of an hour so Robert travels 350 meters because 1400*(1/4)=350
500 + 350 = 850 so Robert is 850 meters ahead when Lionel starts.
Lionel traveling 17km/hr is 3km/hr FASTER than Robert who is going 14km/hr.
That means every hour Lionel is 300 meters closer to Robert.
Use division to see how many times 300meters/hr goes inot 850meters.
850/300 = 2 and 5/6 hours,
so the answer is 2 hours and 50 minutes.