Math Is Fun Forum

  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 2007-05-28 01:48:43

pointblank
Member
Registered: 2007-05-28
Posts: 3

Bulb Problem

One good brain teaser

There is a bulb on first floor and switch is at ground floor . You can not see the bulb or light from that bulb from ground floor. You can not tell from ground floor if the bulb is on or off.

There are three switches on ground floor. Out of these three switches one belongs to the bulb at first floor.

You need to find out correct switch, but you are allowed to go only once at first floor .

Can you guess how to solve it ?

?????

?????

PB

Offline

#2 2007-05-28 02:41:32

Identity
Member
Registered: 2007-04-18
Posts: 934

Re: Bulb Problem

What you do I think, is that you flick the 1st switch, then turn it off and flick the 2nd switch, leaving the 2nd switch on. Then, go upstairs and check on the lightbulb. If the lightbulb is on, then obviously the 2nd switch is correct. If the lightbulb is off, but still hot, then it is the first switch. If the lightbulb is off and cool, then it must be the 3rd switch.

Offline

#3 2007-05-28 13:20:22

pointblank
Member
Registered: 2007-05-28
Posts: 3

Re: Bulb Problem

Identity wrote:

What you do I think, is that you flick the 1st switch, then turn it off and flick the 2nd switch, leaving the 2nd switch on. Then, go upstairs and check on the lightbulb. If the lightbulb is on, then obviously the 2nd switch is correct. If the lightbulb is off, but still hot, then it is the first switch. If the lightbulb is off and cool, then it must be the 3rd switch.

that is right .

cheers

PB

Offline

Board footer

Powered by FluxBB