Ans is B 30
since AB is equal to the radius of the circle triangle OAB is equilateral. hence angle AOB is 60
x=1/2*angle AOB=30
BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
Redeem
Featured Course
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
readyforgmat geometry problem
Source: Beat The GMAT — Problem Solving |
I understand the equilateral part. But, how is x=1/2*angle AOB=30. Which property is this? Yes, the answer is Bliferocks wrote:Ans is B 30
since AB is equal to the radius of the circle triangle OAB is equilateral. hence angle AOB is 60
x=1/2*angle AOB=30
Here, the AB is equal to the Radius. So if we draw a triangle with AB as the base and the third vertex as the centre O, we get a triangle AOB. Now Angle x and Angle AOB is made by the same base AB.
Now we know angle at the centre of the circle is twice the angle at the circumference.
or, angle AOB = 2* angle x
Now, triangle AOB is equilateral.
60 = 2*x
or, x=30
Thus B
Now we know angle at the centre of the circle is twice the angle at the circumference.
or, angle AOB = 2* angle x
Now, triangle AOB is equilateral.
60 = 2*x
or, x=30
Thus B
I still don't get the part about the angle at the center of the circle is twice the angle at the circumference.Nilakshi1001 wrote:Here, the AB is equal to the Radius. So if we draw a triangle with AB as the base and the third vertex as the centre O, we get a triangle AOB. Now Angle x and Angle AOB is made by the same base AB.
Now we know angle at the centre of the circle is twice the angle at the circumference.
or, angle AOB = 2* angle x
Now, triangle AOB is equilateral.
60 = 2*x
or, x=30
Thus B
.I am doing math after 8 years..I want to know the theory ..I know that inscribed angle of a diameter is 90 degrees.this is the theory behind 'the angle at the center of the circle is twice the angle at the circumference'.Let me know if it clarifies the questions.
here angle AOB=2(x+y)=angle ACB
here angle AOB=2(x+y)=angle ACB
Last edited by liferocks on Tue Apr 27, 2010 10:45 pm, edited 1 time in total.
"If you don't know where you are going, any road will get you there."
Lewis Carroll
Lewis Carroll
