Question

1. how many odd numbers of 5 significant digits can be formed with the digits 3,2,7,4,0 when no digit is repeated.

2.in how many can 5 commerce and 4 science students be arranged in a row so that the commerce and the science students are placed alternately

Answer 1

for a number to be odd so we must have 3,7 at the the unit place. so, There are two ways in the unit place

As, the repetition is not allowed, Then ten's place can be filled with any of the remaining 4 digits in 4 ways. Now three digits are left, so hundred's Place can be filled in three ways, Now two digits left. so thousands's place filled in two ways. and

ten thousand's place in one way

=>2*4*3*2*1=48

hence, the way to arrange the required number is 48