Question

On one page of a telephone directory, there are 200 phone numbers. The frequency distribution of their unit's digits is given below:

$\begin{array}{ccccccccccc}\text{Unit's digit}& 0& 1& 2& 3& 4& 5& 6& 7& 8& 9\\ \text{Frequency}& 19& 22& 23& 19& 21& 24& 23& 18& 16& 15\end{array}$

One of the numbers is chosen at random from the page. What is the probability that the unit's digit of the chosen number is (i) 5? (ii) 8?

Answer 1

ANSWER:
Total phone numbers on the directory page = 200
(i) Number of numbers with units digit 5 = 24
Let E 1 be the event that the units digit of selected number is 5.
∴ Required probability = P ( E 1 ) = $\frac{24}{200}=0.12$
(ii) Number of numbers with units digit 8 = 16
Let E 2 be the event that the units digit of selected number is 8.
∴ Required probability = P ( E 2 ) = $\frac{16}{200}=0.08$