Question 41

# A bungalow has one of its room located on the first floor and there are three identical 100 watt electrical bulbs fixed in the room. Each bulb is connected to a specific switch located at the basement. There are only three switches in the basement. All the bulbs are switched off at present and you are also at the basement area. The first floor cannot be seen from the basement area. If you are allowed to use your common prudence, what is the minimum number of times that you will have to go from basement to first floor to identify which switch goes to which bulb?

Solution

Given that there are 3 bulbs and 3 switches.

First, we switch on the first switch and switch it off after some time. And then switch off the second switch and check the basement

The bulb which is off but a little bit warm corresponds to switch 1. The on bulb corresponds to switch 2 and remaining 1 is connected to switch 3.

Hence we need to check only once

• All Quant Formulas and shortcuts PDF
• 170+ previous papers with solutions PDF