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 →

OG PS #32) sqrt[(16)(20) + (8)(32)]?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 99
Joined: Sun Mar 13, 2011 12:42 pm
by factor26 » Sun Jul 31, 2011 12:54 pm
sqrt[(16)(20) + (8)(32)]?


A) 4*sqrt20

B) 24

C) 25

D) 4*sqrt20 + 8*sqrt2

E) 32

OG answer is B.

I tried to prime factorize out;

sqrt [2^4*2^2*5 + 2^3*2^5]

now i'm completely lost on what to do next ... can anyone help?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 99
Joined: Sun Mar 13, 2011 12:42 pm

by factor26 » Sun Jul 31, 2011 1:24 pm
ok i believe i figured this out ... someone correct me if i'm wrong please ...

sqrt[16*20 + 8*16*2]

factor out 16 ...

sqrt[(16) (20 + 8*2)]

sqrt [16*36]

4 * 6

Answer = 24
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 49
Joined: Sun Jun 26, 2011 5:45 pm
Thanked: 2 times

by edge » Sun Jul 31, 2011 1:24 pm
sqrt(16x20 + 16x16) = sqrt(16 x (16 + 20)) = sqrt(16 x 36) = sqrt(16) x sqrt(36) = 4 x 6 = 24
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 312
Joined: Tue Aug 02, 2011 3:16 pmFollowed by: 33 members
Location: New York City
Thanked: 130 times
GMAT Score:780

by gmatboost » Tue Aug 02, 2011 4:51 pm
I happened to post about this question on GMAT Boost: The Blog very recently, check it out:

https://blog.gmatboost.com/2011/08/02/al ... on-5-3-29/
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 31
Joined: Sun Jul 31, 2011 10:55 amFollowed by: 1 member

by HeyArnold » Tue Aug 02, 2011 4:59 pm
My initial strategy for this problem was to factor out a 4..

So

sqrt(16 x 20) + (8 x 32)

becomes 2 x Sqrt(4 x 5) + (2x8)

= 2 x sqrt(36)
=2 * 6 = 12

what is the error in my logic ?!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 19
Joined: Sat Jul 30, 2011 10:39 pm
Location: India
Thanked: 3 times

by Touseef » Wed Aug 03, 2011 9:14 pm
Hey Arnold,

Please understand this logic

16*20=320

can u write 16*20 =4(4*5)=80.That would be wrong.

because a factor of 16 should be taken not 4 to solve this.

Now coming to your question,this is was the error in your logic

sqrt(16 x 20) + (8 x 32)

becomes 2 x Sqrt(4 x 5) + (2x8)

= 2 x sqrt(36)
=2 * 6 = 12

You are actually factoring out 16 but taking it as 4


sqrt[16/4*20/4 + 8/4*32/4] (4*4=16)

=>sqrt[(16) (20 + 8*2)]

sqrt [16*36]

4 * 6

Answer = 24

Hope this helps....
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1