Question

A two digit no. is to be formed from the digits 2,3,5,7,9 repetation of digits is allowed find the probablity that the no. formed is (1)prime number (2) multiple of 3
please give the answer in step by step​

Answer 1

Answer:

Digits are {22,23,25,27,29,32,33,35,37,39,52,53,55,57,59,72,73,75,77,79,92,93,95,97,99}

∴Total digits are 25

Odd numbers are 20

∴ probability that an odd number is formed is

25

20

=

5

4

a multiple of 5

Numbers which are multiple of 5 are

{25,35,55,75,95}

∴ probability of multiple of 5 is

25

5

=

5

1