Question

In how many different ways can the digits 1 through 5,be arranged to form a five digit number.in which,the digits, alternately rise and fall? These numbers are called Mountain Numbers; for example, 13254 is a Mountain number while 12354 is not.

Answer 1

The total possible numbers that can be formed using digits 1 through five are 5*4*3*2*1=120 out of which 24 are the mountain numbers.