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

There are 90 discs numbered from 1 to 90  are placed in a box.
Total number of outcomes = 90

i) There are 81 numbers of two digit number
10, 11, 12, 13, 14 …….. 90

Number of favourable outcomes= 81

Probability = Number of favourable outcomes/ Total number of outcomes
P(two digit number) = 81/90 = 9/10

ii) There are 9 numbers which are a perfect square.
1,4,9,16,25,36,49, 64, 81

Number of favourable outcomes= 9

Probability = Number of favourable outcomes/ Total number of outcomes
P(perfect square number) = 9/90=  1/10

iii)There are 18 numbers which are divisible by 5.
5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90

Number of favourable outcomes= 18

Probability = Number of favourable outcomes/ Total number of outcomes
P(divisible by 5) = 18/90= ⅕.

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