Question

A box contains 90 discs which are numbered from 1 to 90. If one disc 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.

Answer 1

(i) 10,11,12 … 90 are two digit numbers. There are 81 numbers. So, Probability of getting a two-digit number 

\(\frac{81}{90}=\frac{9}{10}\)

(ii) 1, 4, 9,16,25,36,49,64,81 are perfect squares. So, Probability of getting a perfect square number. 

\(\frac{9}{90}=\frac{1}{10}\)

(iii) 5, 10,15 ... 90 are divisible by 5. There are 18 outcomes. So,Probability of getting a number divisible by 5. 

= \(\frac{18}{90}=\frac{1}{5}\)