sum of an arithmetic sequence = (first term + last term)/2 * (number of terms)
I tried using it to find the sum of the positive odd integers less than 100, and my calculator gave me 1, which is definitely not the sum. Can someone show me an example using this formula in action?
As a tutor, I've seen this problem like 10 times without thinking of this. Oh well...
In an election, 2.8 million votes were cast and each vote was for either Candidate I or Candidate II. Candidate I received 28,000 more votes than Candidate II. What percent of the 2.8 million votes were cast for Candidate I?
Okay, this is from Gruber's Complete SAT Math Workbook, page 242, question #6. I'll write the question anyway in case you don't have the book.
Mr. Smith drove from point A to point B in 2 hours. He drove back from point B to point A in 3 hours. If the distance from point A to point B is 100 miles, what is Mr. Smith's average speed for the entire trip?
The first time I did this, I got the answer right, which is 40 miles. But then, several weeks later I went back to do it again and completely forgot how to solve it. No matter what method I try, I always end up getting either 20 or 24. Cam someone show me how to to this step by step?