A box contains 90 discs, numbered from 1 to 90. If one disc is drawn at random from the box, the probability that it bears a prime number less than 23, is:
790
445
989
1090
Solution:
Number of total discs in a box = 90 Number of discs having prime number less than 23 is 8 i.e 2, 3, 5, 7, 11, 13, 17, 19 Therefore, required probability = 8/90 = 4/45