Mastering Riddles and Logical Puzzles: A Thread on Problem-Solving Strategies

Hi, here I am posting a riddle. Find out the answer.

In the basement, there are 3 light switches in the off position. Each switch controls 1 of 3 light bulbs on the floor above. You may move any of the switches, but you may only go upstairs one time. How can you determine which switch controls each light?

Hi Kavita,

Consider S1, S2, and S3. First, switch on S1 and wait for some time, then switch it off. Next, switch on S2 and then come down.

1. Just touch the bulb. If you feel warmth from the bulb, then the corresponding switch is S1.
2. If the bulb was glowing when coming down, then the corresponding switch is S2.
3. Otherwise, it is S3.

Try this:

You have 8 marbles. Out of the 8 marbles, there is one marble that weighs slightly heavier than the rest. The rest of the marbles all weigh the same. How would you find the heaviest marble when you can only weigh them two times using a liberty scale?

First, select 6 marbles from 8 and put 3 marbles on both sides of the liberty scale. If they balance, put the two balanced marbles on the liberty scale. The marble that goes down will be the heavy marble. If either side goes down during the first step, use the 3 marbles from the side that went down. Select any 2 marbles from those 3 and place one marble on each side. If one side goes down, that will be the heavy marble. If they balance, the other remaining marble will be the heavy marble. :-P:-P:-P

Hi Kavita,

I got the answer for this too.

Case 1:

First, keep 6 marbles (3 on each side). If those weigh the same, then weigh the remaining two (one on each side). Now you can identify which one is slightly heavier.

Case 2:

First, keep 6 marbles (3 on each side). If one side of the scale goes down, then obviously we can say that the heavier marble is on that side. Now consider those 3 marbles alone. Among those 3 marbles, keep 1 outside of the scale and the remaining 2, keep 1 on each side. If the scale weighs the same, then the marble outside is heavier; otherwise, one of those 2 which is in the lighter scale.