Quote:
Two siblings Mark and Steve start from the same point and walk in the same direction at speeds of 5 kilometres per hour and 10 kilometres per hour respectively. After walking for an hour, Mark turns around and walks back along the same path to the starting point. Mark rests for half an hour at the starting point, and then hires a taxi driving at 30 kilometres per hour to catch up with Steve. If the taxi charges $10 for the first 2 kilometres and $2 for every subsequent 500 metres, how much in dollars does Mark pay for the taxi ride?
A. 92
B. 102
C. 142
D. 152
E. 160
First, let's calculate the distance covered by Steve till the time Mark hires the taxi.
No. of hours after which the taxi is hired = 2.5
Distance covered by Steve (D) = 10 x 2.5 (Speed x Time) = 25 kilometers
Now, to calculate the amount paid by Mark to the taxi driver, we need to know the distance travelled.
The info that is given to us -> Mark only uses the taxi to catch up with Steve.
So the time travelled for both Mark in the taxi and Steve will be the same when Mark catches up with Steve.
D = S x T
T = \(\frac{D}{S}\)
T (Mark in taxi) = T (Steve)
Let distance be xT (Mark in taxi) = \(\frac{x}{30}\)
T (Steve) = \(\frac{(x-25)}{10}\) ->
(As Steve has already covered 25 kilometers)Equating the two we get:
\(\frac{(x-25)}{10}\) = \(\frac{x}{30}\)
\(20 x = 750\)
\(x = 37.5\)
Distance travelled by Mark in taxi = \(x\) = 37.5 kilometers
Amount paid = 10 + \((x-2)\)*2*2
(Remaining distance multiplied by 2 as the rate after the first 2 kilometers is given per 500 meters)= 10 + (35.5*4)
= 10 + 142
= $152
Option D