My question is what is the formula for adding up numbers when you don't start with number 1? For example 3 + 4 + 5 + 6 = 18. But how could you arrive at the answer without adding all the numbers?
I'm sure this is a very basic math puzzle, but I don't have a strong background in math. The question just came up at work today, so I thought I would try to find out.
You're right about your formula and not only that if you look at your email you'll also see that you have the answer to your question. Suppose I asked you to add up all the numbers from 7 to 1000. Your answer for the sum from 1 to 1000 includes the sum from 1 to 6. If you subtract the two answers you have the sum of 7 + 8 + ... + 1000; it's
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