How do you find the sum of the series $1$ $1$ from i=1 to 42?

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Answer 1 · 2016-10-16T08:33:38

You have to use the formula for the sum:

$1+2+3+ ...+n=sum_(i=1)^(i=n) i=(n*(n+1))/2$

So:

$1+2+3+ ...+42=sum_(i=1)^(i=42) i=(42*(42+1))/2=21*43=903$

How do you find the sum of the series 111 from i=1 to 42?