the sum of the integers from 1 to 10, inclusive, is 55. What is the sum of the multiples of 5 from 5 to 50 inclusive?

Question

Which equation would I use?

Answer 1

Wait is the answer 275? First i use the term equation to find 10 terms then I use the sum equation to find the sum right?

Answer 2

Yes, you are adding
5+10+15+...+45+50
here a=5 and d = 5
How many terms are there?
term(n) = a+(n-1)d
50 = 5 + (n-1)(5)
45 = 5n - 5
50 = 5n
n = 10

so we want the sum of 10 terms
sum = (10/2)(first + last)
= 5(5+ 50) = 275

Answer 3

or, you can think of it as

5+10+...+50 = 5(1+2+...+10) = 5*55 = 275

Answer 4

I like Steve's thinking, but sometimes I like to take a hammer to a thumbtack.