Question

A number is called a “decreasing number” if each digit in the number is less than the digit to its left. For example, 87420 is a decreasing number. How many decreasing numbers are there?

Answer 1

Explanation:

10C5

= 10!/(5!5!)

= 10 . 9 . 8 . 7 . 6 / 5 . 4 . 3 . 2 . 1

= 252 numbers

Subject : Mathematics

Level : SHS

Chapter : Combination