The sum of all positive integers less than 400 which are divisible by 5.

sum = 15800

Step-by-step explanation:

The sum of all positive integers less than 400 which are divisible by 5. The last number divisible by 5 that is less than 400 is 395.

Arithmetic progression can be used to solve this. We will first find the number of term that can give us 395 since that is the last term that is less than 400 and can divide 5.

first term = 5

difference = 5

n = number of terms

nth term = a + (n - 1) d

395 = 5 + (n - 1) 5

395 = 5 + 5n - 5

395 = 5n

n = 395/5

n = 79

The sum of this term can be computed as

sum = n/2 (a + l)

a = first term

l = last term

sum = 79/2 (5 + 395)

sum = 79/2 * 400

sum = 31600/2

sum = 15800

Answer: 8000

Step-by-step explanation:

5+15+25+35 + ... 395

=5 (1+3+5+7 + ... + 79)

=5*40^2

=8000