Riddle: Which Is The Right Switch?

Submitted by: Haim Soleimani

Four switches can be turned on or off. One is the light switch for the incandescent overhead light in the next room, which is initially off, but you don’t know which. The other three switches do nothing. From the room with the switches in it, you can’t see whether the light in the next room is turned on or off. You may flip the switches as often and as many times as you like, but once you enter the next room to check on the light, you must be able to say which switch controls the light without flipping the switches any further. (And you can’t open the door without entering, either!) How can you determine which switch controls the light?

Last Month’s Riddle: Maximum Product

Use all the digits from 1 to 9 without repeating, to form two numbers such that their product is maximum.  A digit used should be unique across both the numbers.  For example, the numbers formed could be 1234 and 56789.

Solution: 9,642  x 87,531=843,973,902

Solved by: Michael Rosen, Victor Grazi

Junior Riddle: Two words

Submitted by: Sarah Dweck

My answer is only two words.

To keep me, you must give me.

Last Month’s Junior Riddle: To Get to the Other Side

Jake was standing on one side of the river, and his dog Scruffy was standing on the other side. “Come on Scruffy, come, boy!” shouted Jake. Scruffy crossed the river and got a treat for being a good dog. The amazing thing was that there was no bridge or tunnel and Scruffy didn’t even get wet! How did Scruffy do it?

Solution: The River was frozen.

Solved by: Kim & Zach Djouejati, Rachel Cohen, Ezra Dayan, Yosef Trachtenberg & Sora Trachtenberg, Pesach Chesir