The conversation between human and AI assistant.
What is the sum of the positive integers less than 150 but greater than 20 that are divisible by 7?
That makes sense. Is there a faster way to calculate the sum without using the formula?
One way to do it is to use a calculator or a spreadsheet. You can simply list out all the numbers that are divisible by 7 between 21 and 147, and then add them up. But that would take a lot of time and effort. Using the formula is much faster and more efficient.