Question

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

Units digit	0	1	2	3	4	5	6	7	8	9
Frequency	19	22	23	19	21	24	23	18	16	15

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

Answer 1

Total phone numbers on the directory page = 200

(i) Number of numbers with units digit 5 = 24

Let E₁ be the event that the units digit of selected number is 5.

∴ Required probability = P(E₁) = $\frac{24}{200}=0.12$

(ii) Number of numbers with units digit 8 = 16

Let E₂ be the event that the units digit of selected number is 8.

∴ Required probability = P(E₂) = $\frac{16}{200}=0.08$