(Q16). 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 :

Total number of discs in the box = 90

∴ Number of total outcomes in drawing a disc at random from the box = 90.

(i) Number of 2-digit numbers in the box =

i.e., Number of favourable outcomes in drawing a 2 - digit numbers =

∴ Probability of selecting a disc bearing a 2 - digit number

=
No. of favourable outcomes
No. of total outcomes
 =
90
 =
10
 =

(ii) Number of perfect squares in the box =

i.e., Number of favourable out-comes in drawning a disc bearing a perfect square =

∴ Probability of drawning a disc with a perfect square =
No. of favourable outcomes
No. of total outcomes
 =
90
 =
10

(iii) Number of multiples of 5 from 1 to 90 are =

i.e., Number of favourable outcomes in drawing a disc with a multiple of 5 =

∴ Probability of drawning a disc bearing a number divisible by 5 =
No. of favourable outcomes
No. of total outcomes
 =
90
 =
5