The first one is geometric sequence
Sn = a (1-r^n)/1-r
where a = 1/2 r = -1/2 and n = 10
So its between 1/4 and 1/2 thats D
The second one uses the length of the arc
= x/360*2 pi * r
We know x = 90 and r = 100 so
length = 100 + 100 + length that is 157 approx C
BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
Redeem
Target Test Prep GMAT OnDemand
Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.
- 715+ score guarantee — highest in the industry (99th percentile)
- 52 chapters · 1,500+ lessons · 4,000+ practice questions
- 400 hours of video · 1,500+ instructor-led HD smartboard lessons
- 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
- 24/7 live support + weekly Zoom office hours with GMAT instructors
- TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
- 1,200+ flashcards + AI-powered study assistant & daily calendar
- OnDemand, LiveTeach & GMAT Bootcamp formats available
- Also: GRE, SAT Math & Executive Assessment courses
- MBA Admissions Consulting now available
- 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
- 200,000+ students served
- 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★
5.0
(559 reviews)
130-pt guarantee
$0 to start
then $127/mo
help on these please
Source: Beat The GMAT — Problem Solving |
can you show me how you solved this:
Sn = a (1-r^n)/1-r
where a = 1/2 r = -1/2 and n = 10
So its between 1/4 and 1/2 thats D
for the 2nd question, how did you get arc =157?
I thought the formula for the arc length was:
(central angle/360)=(arc/circumference)?
thanks
Sn = a (1-r^n)/1-r
where a = 1/2 r = -1/2 and n = 10
So its between 1/4 and 1/2 thats D
for the 2nd question, how did you get arc =157?
I thought the formula for the arc length was:
(central angle/360)=(arc/circumference)?
thanks
1. https://www.beatthegmat.com/integer-gmat ... html#23503
2. r = 100
The perimeter of the circle = 2 * pi * r = 2 * 3.14 * 100 = 628
Since the Angle given is 90, the length of the Arc will be 628/4 = 157
Now the Length of the fence = 100 + 100 + 157 = 357
2. r = 100
The perimeter of the circle = 2 * pi * r = 2 * 3.14 * 100 = 628
Since the Angle given is 90, the length of the Arc will be 628/4 = 157
Now the Length of the fence = 100 + 100 + 157 = 357


















