Number System
A number consists of 3 digit whose sum is 10. The middle digit is equal to the sum of the other two and the number will be increased by 99 if its digits are reversed. The number is:
Let the middle digit be x. Then, 2x = 10 or x = 5.So, the number is either 253 or 352. Since the number increases on reversing the digits, so the hundred's digit is smaller than the unit's digit. Hence, required number = 253.
Total balls = 5 + 4 + 4 = 13∴ n(S) = 13C3 = 2862 blue balls can be selected from 4 balls in 4C2 = 6 ways and the remaining one ball is to be selected from 9 balls in 9C1 = 9 ways ∴ n(E) = 6 x 9∴ P(E) = 6 x 9/286 = 27/143
EXAMIANS