Question

How many numbers of three digits can be formed using the digits 1, 2, 3, 4, 5, without repetition of digits. How many of these are even.

Answer 1

Three places are to be filled with 5 different objects. 

∴ Number of ways = ⁵P₃ = 5 × 4 × 3 = 60 

For the 2nd part, unit digit can be filled in two ways & the remaining two digits can be filled in ⁴P₂ ways. 

∴ Number of even numbers = 2 × ⁴P₂ = 24