Question

2. On a 120km road, a car travels the first 30km with at a uniform speed of 30km/h. How fast must the car travel for the rest of track so as to have an average speed of 60km/h for the entire journey?

Answer 1

HEYA MATE,

HERE IS UR ANSWER.

Thanks for asking this question.

For these sort of questions you have to look at the time involved. If the person wants to average 60 km/hr for a 120 km trip then it has to take exactly 2 hours. At 30 km/hr for the first 30 km it took an hour. This means the rest of the trip, which is 90 km, has to be covered in the remaining hour. The answer is 90km/hr.

I HOPE IT HELPS U.

Answer 2

Let the speed of the car to travel 90km be x km/h.
The speed of car traveling the first 30km = 30km/h

Therefore,
$\frac{30}{30} + \frac{90}{x} = \frac{120}{60} \\ = > 1 + \frac{90}{x} = 2 \\ = > \frac{x + 90}{x} = 2 \\ = > x + 90 = 2x\\ = > x - 2x + 90 = 0 \\ = > - x = - 90 \\ = > x = 90$
Hence, the car must travel in the speed of 90km/h for the reat track so that the average speed is 60km/h.

Hope it'll help u...