Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: Quick tips for adding numbers x to y [#permalink]
10 Jun 2009, 21:58

1) Add the numbers from 40 to 70, inclusive. Formula for sum of first N natural numbers is = N(N+1)/2 Sum from 1 to 70 Sa= 70*71/2 Sum from 1 to 40 Sb= 40*41/2 So sum from 40 to 70 = Sa-Sb

2) Add the even numbers from 40 to 70, inclusive. 3) Add the odd numbers from 40 to 70, inclusive.

========================

As a general solution to all these kind of problems learn the AP series. google on Arithemic Progression series. It is kind of difficult to write the formula here but all these calculations are tooooooo simple using this series.

Re: Quick tips for adding numbers x to y [#permalink]
12 Jun 2009, 13:34

5

This post received KUDOS

1

This post was BOOKMARKED

If you don't mind remembering a formula or two then yes you can. The examples that you have given can be grouped under Arithmetic Progressions...or a finite sequence of evenly spaced numbers.

There are two formulas:

\(1. S = \frac{n}{2} [2a + (n-1)d]\)

where \(S=\text{sum of the all the numbers in the sequence}\) \(n=\text{total number of numbers in the sequence}\) \(a=\text{the first number of the sequence}\) \(d=\text{the different between any two consecutive numbers in the sequence}\)

\(2. S = \frac{n}{2} [\text{First Term}+\text{Last Term}]\)

where \(S=\text{sum of the all the numbers in the sequence}\) \(n=\text{total number of numbers in the sequence}\)

You can use either equation based on what is provided in the question.

Lets take your examples and solve them. For all of these we know the first and the last number so we should be fine with equation 2.

1) Add the numbers from 40 to 70, inclusive. Solution: Here the sequence is 40,41, 42, ...., 69, 70. To calculate n \(n=\text{Last number}-\text{First number} + 1\)

2) Add the even numbers from 40 to 70, inclusive. Here the sequence is 40,42, 44, ...., 68, 70. Solve using 40 as the first term and 70 as the last term To calculate n for even (or odd) number

Re: Quick tips for adding numbers x to y [#permalink]
03 Feb 2015, 11:25

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Michigan Ross: Center for Social Impact : The Center for Social Impact provides leaders with practical skills and insight to tackle complex social challenges and catalyze a career in...

The following pictures perfectly describe what I’ve been up to these days. MBA is an extremely valuable tool in your career, no doubt, just that it is also...