What is the sum of all consecutive multiples of 8 between 400 and 600, inclusive?

Incorrect.
[[Snippet]]

Incorrect.
[[Snippet]]

Incorrect.
[[Snippet]]

Incorrect.
[[Snippet]]

Correct.
[[Snippet]]
Both 400 and 600 are multiples of 8, so use them as the first and last multiples in the range. First calculate the number of terms:
1. Subtract the extremes:
>>$$600 - 400 = 200$$
2. Divide by 8:
>>$$\frac{200}{8} = 25$$
3. Add 1:
>>$$25 + 1 = 26$$
Then calculate the average:
>$$\text{Average} = \frac{400 + 600}{ 2} = \frac{1{,}000}{2} = 500$$
Finally, multiply the number of terms by the average:
>$$\text{Sum} = 26 \times 500 = 13{,}000$$

8,000

10,400

12,500

13,000

15,000