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

Answer:

1. 81/90

2.1/10

3.1/5

Step-by-step explanation:

1. there are a total of 81 two-digit numbers  to pick a disc of this type the probability will be (81 C1)/(90C1)

=81/90

2. there are a total of 9 perfect squares which are 1,4,9,16,25,36,49,64,81

to pick a disk of this type the probability will be (9C1)/(90C1)

=9/90

=1/10

3. for a number divisible by 5 the units digit of that number should be either 5 or 0, from 1-10 there are two numbers which are divisible by 5 so for 90 numbers there will be 18 digits that are divisible by 5.

the probability will be (18C1)/(90C1)

=18/90

=1/5