Question

Question 18 (i)
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

Total number of outcomes = 90
Number of one-digit numbers from 1 to 90 are 9.
Number of two-digit numbers from 1 to 90 = 90 - 9 = 81
$\therefore$ Favourable outcomes = 81
Hence, P (getting a disc bearing a two-digit number)
$=\frac{81}{90}=\frac{9}{10}$