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

Redeem
TTP OnDemand GMAT Video Course
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
Start Free 5-Day Trial Read 559 Reviews →

Surface of a certain planet

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 941
Joined: Sun Dec 27, 2009 12:28 amFollowed by: 1 member
Thanked: 20 times
by bhumika.k.shah » Fri Jan 22, 2010 2:08 am
The surface of a certain planet reflects 80 percent of the light that strikes it. The clouds
around the planet then absorb 40 percent of the reflected light. What percent of the light
that strikes the planet is reflected from the surface and passes through the clouds without
being absorbed?

A.32%
B.40%
C.48%
D.60%
E.88%

OA C

how ??? me getting E :(
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members
Thanked: 137 times

by thephoenix » Fri Jan 22, 2010 2:26 am
let x be the amnt of light striking

then 0.8x is the amnt of light being reflected

and 0.4*0.8x=0.32 x is the amnt of light being absorbed

and therefore 0.8x-0.32x=0.48x is the amnt of light passing through (or not getting absorbed)

%=0.48x/x=48 ( edited)

IMO C
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
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 » Fri Jan 22, 2010 3:18 am
bhumika.k.shah wrote:The surface of a certain planet reflects 80 percent of the light that strikes it. The clouds
around the planet then absorb 40 percent of the reflected light. What percent of the light
that strikes the planet is reflected from the surface and passes through the clouds without
being absorbed?

A.32%
B.40%
C.48%
D.60%
E.88%

OA C

how ??? me getting E :(
I don't really agree with the OA here.

If 100 is incident, 80 is reflected immediately; and 40 percent of 80 that is 32, gets absorbed in the clouds thereby enabling the remaining 48 out of 80, which is (48/80) × 100 = 60 percent of the light that strikes the planet and is reflected from the surface and passes through the clouds without being absorbed.

Mind what is in bold here. Read again-it clearly asks us about the fraction of light that finally come out of the clouds out of what has been first reflected from the planet from all the incident light.

I'll go with [spoiler]D[/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
Legendary Member
Posts: 941
Joined: Sun Dec 27, 2009 12:28 amFollowed by: 1 member
Thanked: 20 times

by bhumika.k.shah » Fri Jan 22, 2010 3:23 am
its a plain wordy problem.thats why it seems soo confusing.
its saying planet absorbs 40% of the reflecting light. which means it doesn't absorb the remaining 60% of the light tht is getting reflected.

let the light strike = 100
therefore 80% of it tht is reflected will be = 80
40% of the light tht is reflected is getting absorbed = 40% of 80 = 32

therefore of the light tht is reflected , 60% is not getting absorbed = 60% of 80 = 48

the question asks what % of the light that is striking is reflected but not getting absorbed = 48/100 = 48%

Hence Answer C :D
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
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 » Fri Jan 22, 2010 3:25 am
bhumika.k.shah wrote:The surface of a certain planet reflects 80 percent of the light that strikes it. The clouds around the planet then absorb 40 percent of the reflected light. What percent of the light that strikes the planet is reflected from the surface and passes through the clouds without being absorbed?
A.32%
B.40%
C.48%
D.60%
E.88%

OA C

how ??? me getting E :(
I don't really agree with the OA here.

If 100 is incident, 80 is reflected immediately; and 40 percent of 80 that is 32, gets absorbed in the clouds thereby enabling the remaining 48 out of 80, which is (48/80) × 100 = 60 percent of the light that strikes the planet and is reflected from the surface and passes through the clouds without being absorbed.

Mind what's in bold above. Read it again-it clearly asks for the fraction of light that has finally come out of clouds without being absorbed, out of what has been first reflected from the planet surface from all the light that was made incident to it.

I'll go with [spoiler]D[/spoiler] here.
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
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 » Fri Jan 22, 2010 3:28 am
sanju09 wrote:
bhumika.k.shah wrote:The surface of a certain planet reflects 80 percent of the light that strikes it. The clouds
around the planet then absorb 40 percent of the reflected light. What percent of the light
that strikes the planet is reflected from the surface and passes through the clouds without
being absorbed?

A.32%
B.40%
C.48%
D.60%
E.88%

OA C

how ??? me getting E :(
I don't really agree with the OA here.

I'll go with [spoiler]D[/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
Legendary Member
Posts: 941
Joined: Sun Dec 27, 2009 12:28 amFollowed by: 1 member
Thanked: 20 times

by bhumika.k.shah » Fri Jan 22, 2010 3:28 am
kindly read my post above and let me know if u still need some more explanation
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
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 » Fri Jan 22, 2010 3:31 am
NOW I AGREE

SO WHAT?
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
Legendary Member
Posts: 941
Joined: Sun Dec 27, 2009 12:28 amFollowed by: 1 member
Thanked: 20 times

by bhumika.k.shah » Fri Jan 22, 2010 3:32 am
hence the answer is C - 48% :-P
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
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 » Fri Jan 22, 2010 3:34 am
bhumika.k.shah wrote:hence the answer is C - 48% :-P
GEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE MAAAAAAAAAAAAAAAAAAAAAAAAAAM
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
Master | Next Rank: 500 Posts
Posts: 233
Joined: Mon Jun 09, 2008 1:30 am
Thanked: 5 times

by blaster » Fri Jan 22, 2010 4:45 am
take for example 100

80% of 100 is 80
then 40% of 80 is 32

the final step 80-32=48
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1