30 apples = 100paise
he want 20% profit from 100 paise
20% profit in 100 paise is 20 paise
so now he planned to sell 30 apples for 100+20=120 paise
now the rate of 1 apple =120/30=4paise
for 100 paise =100/4=25.
let s.p of 'x' apples=100p
also,SP = 1.20 OF CP
THEREFORE,CP of 'x' apples = 100/1.20=83.3333p
COST OF 1 APPLE=3.33p(30 apples in 100p)
no. of apples bought in 83.33p=(83.33/3.33)=25
Outside a room there are three light switches. Each switch
is connected to a different light bulb inside the room.
Each of the three switches can be either 'ON' or 'OFF'.
You are allowed to set each switch the way you want it,
once, and then enter the room.
Your task is to then determine which switch controls which
bulb. How can you do it?