Question

In class we are using special sum formulas but don't know how to get the answer for this question

Answer 1

You are referring to:


`\sum\limits_(i=1)^(n){i} = (n(n+1))/(2)`

You can solve your problem by calculating


`\sum\limits_(i=1)^(525){i} = (525\cdot526)/(2) = 138075`

and then subtracting the first bit:


`\sum\limits_(i=1)^(19){i} = 190`

So 138075 - 190 = 137885