A motor car starts with a speed of 70 kmph with its speed increasing every two hours by 10kmph. In how many hours will it cover 345 kms?

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answer is C.

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Detailed Solution

Concept- First let us find the distance the car traveled when the speed is 70 kmph. By using the formula i.e.

We can find the distance it traveled in the first interval.
The speed increased by 10kmph every two hours, so let us find the distance it traveled during this interval. In order to find the distance it traveled in the third interval we need to subtract the distance it traveled in the first two intervals from the total distance to be covered. With this we get the distance of the third interval.
We know that the speed increases by 10 kmph so the speed of this interval is 90 kmph. By this we will now calculate time taken to cover this distance.
We were asked to find the total time taken to cover 345 kms so, we can add the time taken in all the three intervals and we get

Distance to be covered = 345 kms
Distance covered when speed is 70 kmph