A car is driven up the mountain with the speed 30 kmph while it is drove down from the top at the speed of 45 kmph. What would be the average speed?A)20kmphB)40kmphC)36kmphD)50kmph
Question
A car is driven up the mountain with the speed 30 kmph while it is drove down from the top at the speed of 45 kmph. What would be the average speed?A)20kmphB)40kmphC)36kmphD)50kmph
Solution
The average speed is not simply the average of the two speeds. Instead, it is the total distance divided by the total time.
The total distance is twice the distance up or down the mountain (since the car goes up and then down).
Let's assume the distance up the mountain (or down) is 'd' km. So, the total distance = 2d km.
The time taken to go up the mountain = d/30 hours, and the time taken to go down = d/45 hours.
So, the total time = d/30 + d/45 = (3d + 2d) / 90 = 5d/90 = d/18 hours.
Therefore, the average speed = total distance / total time = 2d / (d/18) = 36 kmph.
So, the correct answer is C) 36 kmph.
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