AllExperts > Advanced Math 
Search      
Advanced Math
Volunteer
Answers to thousands of questions
 Home · More Advanced Math Questions · Answer Library  · Encyclopedia ·
More Advanced Math Answers
Question Library

Ask a question about Advanced Math
Volunteer
Experts of the Month
Expert Login

Awards

About Us
Tell friends
Link to Us
Disclaimer

 
 
 
 
About Paul Klarreich
Expertise
I can answer questions in basic to advanced algebra (theory of equations, complex numbers), precalculus (functions, graphs, exponential, logarithmic, and trigonometric functions and identities), basic probability, and finite mathematics, including mathematical induction. I can also try (but not guarantee) to answer questions on Abstract Algebra -- groups, rings, etc. and Analysis -- sequences, limits, continuity. I won't understand specialized engineering or business jargon.

Experience
I taught at a two-year college for 25 years, including all subjects from algebra to third-semester calculus.

Education/Credentials
-----------

 
   

You are here:  Experts > Science > Mathematics > Advanced Math > Telescoping sum

Advanced Math - Telescoping sum


Expert: Paul Klarreich - 10/10/2009

Question
calculate the sum of 1 -2 +3 -4 +5 -6 +7 -8........+19 -20

Answer
Questioner: kevin
Country: United Arab Emirates
Category: Advanced Math
Question: calculate the sum of 1 -2 +3 -4 +5 -6 +7 -8........+19 -20
...........................................
This is called a 'telescoping sum', or something like that.  Let's parenthesize it:

(1 - 2) + (3 - 4) + (5 - 6) + (7 - 8) + ........ + (19 - 20)

Each grouping adds to -1, and there are ten of them.

Does that do it for you?  

Add to this Answer   Ask a Question


 
User Agreement | Privacy Policy | Kids' Privacy Policy | Help
Copyright  © 2008 About, Inc. AllExperts, AllExperts.com, and About.com are registered trademarks of About, Inc. All rights reserved.