Math help please!?

Question

In an exceptionally long corridor in a Space Station, there are one thousand windows along one wall. Coincidentally, there are exactly one thousand people in the station. Dr Man orders the first person to open the blinds on every window. Then, he orders the second person to close the blinds on every second window. Then the third person is told to go to every third window, and close the blinds if they are open, and open the blinds if they are closed. The fourth person does this for every fourth window, and so on. After all 1000 people complete the process, how many blinds are open?

Answer 1

31 Blinds Open

Answer 2

1

Answer 3

Count all of the prime numbers between 1 and 1000 (you include 1) to get your answer. So, you would count 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, etc. You get the point.

This works because, since prime numbers have an odd number of factors, the prime-numbered blinds will be left open.

P.S. A shorter way to find the number of prime numbers between 1 and 1000 is to take the square root of 1000, which is approx. 31.6 and round DOWN. That would mean that 31 blinds would be open.

This works because there can't be negative-numbered windows and since there are only 1000 windows the square numbers after 31 squared would be larger than 1000. For example 32 squared = 1024.

So, 31 blinds would bo open since there are 31 square numbers between 1 and 1000 (counting 1) : 1 squared (1), 2 squared (4), 3 squared (9), etc. up to 31 squared (961).

Hope this helped. ;-)

Answer 4

Can they open the blinds in a space station

Answer 5

One. The first window. Why is everyone asking this same question for the billionth time this week?

Answer 6

The correct answer is one for 2 points and hopefully it is the best answer for 10.

Answer 7

I think I'll just leave all the windows open... much easier...

Answer 8

i dont know, thats a tough one!!

Answer 9

alot...........???