riddle

[alison6399]

Two cars set off from the same point to travel the same journey. The first car has a start of 1 minute before the second car sets off. If the first car travels at 45Kph & the travels at 60Kph, how many kilometres will be travelled when the cars are equal?

Please explain answer. Thanks

[Gizmonster]

First car sets off and travels 45/60 = 3/4 km before the 2nd one sets off.
2nd car sets off and is travelling 15km/h faster than the 1st one.
It needs to catch up the 3/4 km which it does so in 3 minutes:
distance = velocity x time
3/4 = 15t
t = 3/(4x15)
t = 3/60 hr = 3 minutes

In 3 minutes the first car has travelled:
(45/60 x 3) plus the original 3/4 km start = 9/4 + 3/4 = 3km

Check the answer with the 2nd car:
In 3 minutes, the 2nd car has travelled:
60/60 x 3 = 3 km

...... so the answer you're looking for is 3km