Brainteaser

[apoonia]

U are driving from positioin A to B at a speed of 20kms/hr when u reached half the distance u wanted all ur journey form A to B should be on an average of 40kms/hr so what speed sholud u drive now so that ur average speed for the jouney becomes 40kms/hr ..

a bit tricky.......






Hint: distance is insignificant.......



regards
Amit Poonia

[bnashier]

Very good guestion.

You can't do it. With your hypothesis, you have spent all the time allotted to cover the entire distance only to reach midpoint.

Think of it in a layman's way like this. Suppose the distance is 80 kms. And two guys start their separate cars at the same time. One drives @ 20 kms/hour and the other @ 40 kms/hour. When the 20 kms/hour car reaches the midpoint point in two hours, the other car touches the destination!

For a theoretical possibility to cover a distance (regardless of length of the distance) with a desired overage speed (which is same thing as in a desired amount of time), then you must travel half the distance with more the half the desired average speed (in other words you can't afford to spend all of your time is covering half the distance or less).

Examples.

1. If you wish to cover a distance (any amount) at an average speed of 40 Kms/hour, and you travel the first half @ 30 kms/hour, then you need an average speed of 60 kms/hour over the second half.

2. If you wish to cover a distance (any amount) at an average speed of 50 Kms/hour, and you travel the first half @ 30 kms/hour, then you need an average speed of 150 kms/hour over the second half.

[apoonia]

:rolleyes: great work budh ...................quite impressive