How many numbers can be formed from 1, 2, 3, 4, 5(without repeating), where the digit at the unit’s place must be greater than that in the ten’s place?(CAT 1998)
Option (b)
Case 1- units place= 1 (0 possibilities)
Case 2- units place = 2 (tens place=1 possibility (2) and 3! Arrangements for the remaining places) = 1x3!
Case 3- units place = 3 (tens place=2 possibilities (1,2) and 3! Arrangements for the remaining places) = 2x3!
Case 4- units place = 4 (tens place=3 possibilities (1,2,3) and 3! Arrangements for the remaining places) = 3x3!
Case 5- units place = 5 (tens place=4 possibilities (1,2,3,4) and 3! Arrangements for the remaining places) = 4x3!
Total = 60