Sonali has to cover a distance of 240 km. If she increased her speed by 10 km/hr, she takes 2 hours less time than the usual time. At the usual speed in how much time she will cover a distance of 80 km?
Answer & explanation
Correct answer: option 2
When the distance is same, ratio of speed and time are reciprocal
Let the initila speed be (x) km/hr
Thus ratio of time will (x + 10) : x
Difference = 10R = 2
R = \(\frac{1}{5}\)
Distance = speed x time = (x) x (x + 10) x \(\frac{1}{5}\) = 240
x(x + 10) = 1200
possible values of x = 30, 40
Initial speed = 30 km/hr
At this speed, time taken to cover 80km = \(\frac{distance}{speed}\) = \(\frac{80}{30}\) = 2hr 40 min