vaibhav101 wrote:A motorcyclist rode the first half of his way at a constant speed. Then he was delayed for 5 minutes and , therefore, to make for the lost time he increased his speed by 10 km/hr. Find the initial speed of the motorcyclist if the distance covered by him is equal to 50 km.
A 36 km/hr
B 48 km/hr
C 50 km/hr
D 62 km/hr
E 55 km/hr
We can PLUG IN THE ANSWERS, which represent the initial speed.
When the correct answer is plugged in, increasing the speed by 10 kph will enable the cyclist to travel 25 km in 5 fewer minutes.
Since the increase in the speed and the total distance are both multiples of 10, the correct answer is probably
C, which also is a multiple of 10.
C: initial speed = 50 kph, higher speed = 50+10 = 60 kph
Time to travel 25 kilometers at a speed of 50 kph = d/r = 25/50 = 1/2 hour.
Time to travel 25 kilometers at a speed of 60 kph = d/r = 25/60 = 5/12 hour.
Time difference = 1/2 - 5/12 = 6/12 - 5/12 = 1/12 hour = 5 minutes.
Success!
The correct answer is
C.
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