Question

A bag contains 9 balls marked with the digits 1,2,3.....9. If two balls are drawn from the bag then find the number of ways of getting the sum of digits on the balls as odd?

• A. $4C_1\times 5C1$
• B. $5C1\times 4C2$
• C. $4C1\times 4C1$
• D. $4C1\times 5C2$

Answer 1

The correct option is A $4C_1\times 5C1$

we have set of balls marked 1, 2, 3, 4, 5, 6, 7, 8, 9 on them.
Number of balls marked with odd digits = 5
Number of balls marked with even digits = 4
to make sum of digit odd we need to select one even and one odd number
combination-$4C1\times 5C1$
option (a) is correct