Question: Find a solution for this math problem: A singer has 50 microphones that he wants to arrange in pairs on a stage. While making the arrangement, he realizes that 20% of the microphones won't find any space to fit in after arranging the rest in pairs. How many pairs of microphones was he able to arrange on the stage?
Answer: 
The number of microphones that were not able to find space on the stage is 20/100*50 = 10
This means the singer could set 50-10 = 40 microphones into pairs on the stage.
Since a pair has 2 microphones, the singer set up 40/2 = 20 pairs of microphones on the stage.