Answer:
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
