Question

If number are formed using digits 2,3,4,5,6without repetitions how many of them will exceed 400?

Answer 1

Answer:

There are in total 5 digits, therefore all the five digit numbers will cross 400

Number of five digit numbers that can be formed= 5!= 120

For four digit number= 4×4!= 96

For three digit the number should start with either 4, 5 or 6

Starting with 4 possibilities= 1× 4C2× 2!

                                           = 4!×2!÷(2!×2!)

                                          = 12

Starting with 5 and 6 =12

Total numbers exceeding 400= 12+12+12+96+120 =252