Find the sum of all natural numbers divisible by 8 and not exceeding 80.

To begin with, let’s write out all the numbers that will satisfy the condition of this task, it is obvious that the first will be the number 8, and the last will be the number 80:

8, 16, 24, 32, 40, 48, 56, 64, 72, 80.

Now let’s sum them up in a rational way:

(8 + 72) + (16 + 64) + (24 + 56) + (32 + 48) +40 + 80 = 80 + 80 + 80 + 80 + 120 = 440.

Answer: The sum of all natural numbers that satisfy the condition is 440.



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