Homework finding sums

Question

Can someone explain to me 0/20+1/20+2/20+... 20/20 How do I find the answer?

Answer 1

This is an arithmetic sequence with 21 terms and a common difference of 1/20. We are adding 1/20 to each term to get the next term

The sum of a arithmetic sequence is the average of the first and last terms multiplied by the number of terms

so we have (0+1)/2 x 21= .5(21) = 10.5