A box contains 90 discs which are numbered from 1 to 90. If one discs is drawn at random from the box. find the probability that it bears
(i) a two digit number
(ii) a perfect square number
(iii) a number divisible by 5.
GIVEN: A box contains 90 discs which are numbered from 1 to 90.If one disc is drawn at random from the box
TO FIND: Probability that it bears
(i) a two digit number
(ii) a perfect square
(iii) a number divisible by 5
Total number of discs numbered is 90
(i) disc marked a two digit numbers are 
Total number of disc marked two digit numbers from 1 to 90 are 81
We know that PROBABILITY = 
Hence probability of getting disc marked with two digit numbers from 1 to 90 is 
(ii) disc marked a perfect squared numbers are 1,4,9,16,25,36,49,64,81
Total number of disc marked perfect square numbers from 1 to 90 are 9
We know that PROBABILITY =
Hence probability of getting disc marked with perfect square numbers from 1 to 90 is 
(iii) disc marked with a number divisible by 5 are 5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90
Total number of disc marked perfect square numbers from 1 to 90 are 18
We know that PROBABILITY =
Hence probability of getting disc marked number divisible by 5 from 1 to 90 