Puzzle Time – House Building

If five people can build five houses in five days, how many days does it take 100 people to build 100 houses?

Solution

The statement “five people can build five houses in five days”

Is equivalent to (keep the “time of 5 days fixed” to arrive at this):

“A person can build a house in five days”

Hence,

“2 people can build 2 houses in five days too”

And,

“3 people can build 3 houses in five days”

.
.
.

And so on till,

“100 people can build 100 houses in five days as well”

Thus, Answer (5 days).