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In the video below, Alison works out \(\sum_{i=1}^{10} i\).
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How could you adapt this method to work out the following sums?
After how many terms would $17+21+25+\dots$ be greater than $1000$?
Can you find the sum of all the integers less than $1000$ which are not divisible by $2$ or $3$?
Can you find a set of consecutive positive integers whose sum is 32?