sanjoy18 wrote:A car runs on four tyres and has one extra tyre. If each tyre lasts for 10,000 km then what is the
maximum distance (in km) that the car can travel using the five tyres?
(a) 10,000 (b) 11,000 (c) 12,500 (d) 15,000
Let the 5 tires be = A, B, C, D, E.
If we swap out a tire every kilometer -- so that, for each kilometer traveled, a different tire is not used -- the usage per tire over the first 5 kilometers will look as follows:
A B C D E
1 1 1 1 0
1 1 1 0 1
1 1 0 1 1
1 0 1 1 1
0 1 1 1 1
Result:
Usage per tire = 4 kilometers.
Distance traveled = 5 kilometers.
Implication:
For every 4 kilometers of tire usage, 5 kilometers can be traveled.
Since each tire can be used for up to 10,000 kilometers, we get:
(4 kilometers usage)/(5 kilometers traveled) = (10,000 kilometers usage)/(x kilometers traveled)
4x = 50,000
x = 12,500.
The correct answer is
C.
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