(a) A number divisible by 4 formed by the digits 1,2,3,4 and 5 should have the last two digits 12 or 24 or 32 or 52 . In each cases, the five digit number can be formed using the remaining 3 digits in 3!=6 ways A number divisible by 4 can be formed in 6×4=24 ways Total number of 5 -digit numbers that can be formed using the digits 1,2,3,4 and 5 without repetition 5!=120 Thus, required probability =‌