A policeman chases after a thief who has a 400 KM head start. They run at constant speeds, with the policeman running 10 km every 6 minutes and the thief 10 km every 10 minutes. How long will policeman take to catch up with the thief?
A) 3 hrs
B) 5 hrs
C) 8 hrs
D) 10 hrs
E) 15 hrs
d
Can I have your approach ?
The distance between the policeman and thief is 400 KM.
Policeman’s speed is v=d/t
v=10/(6/60)=10x(60/6)=100 km per hour
Speed of thief
v=10x(60/10)=60
Difference between their speeds is 100-60=40
Thus distance of 400 KM will be covered in 400/40=10 hours
d:
@Erlan,
Good Work !!!
d
We can with answers also…. in one Hour Policeman will cover— 100 KM and thief 60 KM. So in 10 Hours both will be at same distance…
It saves a lot of time. can be ticked in 45Seconds
Yes Rohit,
I agree with you.
Doing the very same thing in more precise way.
Now take the twist.
Lets assume that there is a dog who is also start following the thief along with policeman. First, Dog reach the thief then come back & inform the police & again went back to chase the thief & come back & inform the police. He is keep doing till the time police able to catch the thief.
Now tell me total distance traveled by dog, If his speed is 25 km every 10 minutes.
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simple calculation – dog is running at 150 km/hr and total time taken by police to catch the thief is 10 hrs. so dog covered 150*10 = 1500km in total
Any comments?
@Sunil,
You got the right choice.
D
The answer is D
D)