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 a two-digit number.

Answer 1

We have total number of discs = 90

Total number of possible outcomes = 90

Since the two-digit numbers are 10, 11, 12, ....., 90.

∴ Number of two-digit numbers: 90 − 9 = 81

∴ Number of favourable outcomes = 81

∴ P (getting a two-digit number) = `"Number of favourable outcomes"/"Total number of possible outcomes"`

= `81/90`

= `9/10`