Brain Wars | Episode 2 – Light years?

Question:

Let’s say ISRO discovered life on a planet which is 40 light years away from Earth. So it sent a spacecraft to verify the discovery. The spacecraft can travel with a maximum speed of 70 lightyears/year ( using a Wormhole!) and any change in speed is instantaneous (i.e. time lost in acceleration and deceleration is negligible). At the midway crew members realized that they were traveling at the speed of 20 lightyears/year and decided to speed up the spacecraft. How fast do they need to travel the rest of the course to have an average speed of 40 lightyears/year? Given the speed limits of the spacecraft is it even possible?!

Answer:

Its impossible to have an average speed of 40 lightyears/year.

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Brain Wars | Episode 1 – Shortest possible time [puzzle]

Question:

A family of four members (Father, Mother, Daughter and Son) set up a camp near the bank of a river. At midnight they discovered that the forest behind them has caught fire and is rapidly approaching them. The only choice the family has got is to cross the river (they have a boat which can carry a maximum of two members). All the family members know how to row the boat but with different speeds (Father, Mother, Daughter and Son can row to other side of the bank in 1min, 2min, 5mins and 10mins respectively). The pairs must row at the speed of the slowest person. Also the boat cannot cross the river without a person on it. Given the limitations what is the shortest possible time in which the entire family can safely cross the river?

Answer:
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