BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
GMATLiveTeach Starts Oct 17
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Chris Peckover, 100th-Percentile GMAT Scorer

Oct 17 · Chris Peckover
Sat · 11:00 AM to 2:00 PM ET
Oct 20 · Chris Peckover
Tue, Thu · 8:00 to 10:00 PM ET
Oct 25 · Josh Braslow
Sun · 1:00 to 4:00 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemand 5 seats left Start anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

Arithmetic Progression

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members
Location: India
Thanked: 267 times
GMAT Score:760

by sanju09 » Wed Sep 18, 2013 5:07 am
mgm wrote:Just wondering , what is the best way to solve the following :

What is the sum of sum of odd numbers between 50 and 100 and sum of even numbers between 200 and 300 ?
The features of a series that contains equally spaced terms:

"¢ The average (arithmetic mean) of the series is just the average of its first and last terms.

"¢ The number of terms in the series is one more than the ratio in the difference between last and first term to the equal space size.

"¢ Sum of the series is half the product of number of terms and sum of first and last terms.

With that information, the number of terms in the series 51, 53, 55...99 is 1 more than (99 - 51)/2 or 25, and sum of this series is ½ (25) (51 + 99), which is [spoiler]1875[/spoiler].

Similarly, the number of terms in the series 202, 204, 206...298 is 1 more than (298 - 202)/2 or 49, and sum of this series is ½ (49) (202 + 298), which is [spoiler]12250[/spoiler].

And, finally, sum of the two sums is [spoiler]1875 + 12250 = 14125[/spoiler].
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members
Thanked: 448 times
GMAT Score:650

by theCodeToGMAT » Wed Sep 18, 2013 5:39 am
Use Arithmetic Progression

Sum of ODD Numbers from 50 to 100,
i.e. 51, 53, ... 99

S = n ( 2a + (n-1)d)/2
= 25 ( 2 x 51 + 24 x 2)/2
= 25 x 150 /2
= 1875

Or,

Sum of EVEN Numbers from 200 to 300,
i.e. 202, 204... 298

S = n ( 2a + (n-1)d)/2
= 49 ( 2 x 202 + 48 x 2 )/2
= 49 ( 500 ) /2
= 12250

Total Sum = 1875 + 12250 = 14125
mgm wrote:Just wondering , what is the best way to solve the following :

What is the sum of sum of odd numbers between 50 and 100 and sum of even numbers between 200 and 300 ?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Wed Sep 18, 2013 5:58 am
Another approach for sum of ODD Numbers from 50 to 100,

We want 51+53+55+....97+99

There are 50 numbers from 51 to 100 inclusive (since 100-51+1 = 50)
Half of these numbers are odd and half are even, so we know there are 25 terms in the sum 51+53+55+....97+99

For "fun," let's evaluate (51+53+55+....97+99) + (51+53+55+....97+99), but we'll do so in a useful way:

....51 + 53 + 55 +...+ 97 + 99
.+ 99 + 97 + 95 +...+ 53 + 51
...150+ 150+ 150+...+ 150 + 150

How many 150's do we have in the new sum? There are 25 altogether.
25x150 = 3750

IMPORTANT: Since we've added every term twice, we need to take 3750 and divide by 2 to get 1875

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members
Thanked: 448 times
GMAT Score:650

by theCodeToGMAT » Wed Sep 18, 2013 5:59 am
Another Method:

Sum of First n Even Number: n(n+1)
Sum of First n Odd Number : n^2

Sum of ODD Number between 50 to 100 = (Sum of ODD numbers 0 to 100) - (sum of 0 to 50)
 = 50^2 - 25^2
= (50+25) x ( 50-25)
= 75 x 25 = 1875


Sum of EVEN Number between 200 to 300 = (Sum of EVEN numbers 0 to 300) - (sum of 0 to 200)
 = (149(149+1)) - (100(100+1))
= (149 x 150 - 100 x 101)
= 50 ( 149 x 3 - 2 x 101)
= 50 (245) = 12250
Total Sum = 1875 + 12250 = 14125

mgm wrote:Just wondering , what is the best way to solve the following :

What is the sum of sum of odd numbers between 50 and 100 and sum of even numbers between 200 and 300 ?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1