Question

How many positive numbers from 1 to 999 have the sum of

their digits equal to 8?

For ex. the sum of digits in the numbers 62, 431, ... are equal to 8.

Answer 1

45 positive numbers have the sum of their digits equal to 8

Explanation:

given data

number = 1 to 999

sum n = 8

to find out

positive numbers

solution

we will choose number by this formula

(n+1) (n+2) / 2

here n is 8

so put this value we get number that

positive numbers = (n+1) (n+2) / 2

positive numbers = (8+1) (8+2) / 2

positive numbers = 90 / 2

so 45 positive numbers have the sum of their digits equal to 8