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 →

mixtures - very tough

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 122
Joined: Mon Dec 15, 2008 12:03 am
Thanked: 2 times
by vkb16 » Mon Oct 19, 2009 3:31 am
Some part of a 50% solution of acid was replaced with an equal amount of 30% solution of acid. If, as a result, 40% solution of acid was obtained, what part of the original solution was replaced?

1/5
1/4
1/2
3/4
4/5

Please explain what the qs is asking.. the wording is difficult to understand

OA is c
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Newbie | Next Rank: 10 Posts
Posts: 9
Joined: Wed Oct 07, 2009 8:10 am
Thanked: 2 times

by happybruce » Mon Oct 19, 2009 4:32 am
just looking at the numbers alone, i'd say the answer is 1/2(="c") b/c only when 1/2 of 50% solution is mixed with 1/2 of 30% solution, one will get a whole of 40% solution.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 76
Joined: Sat Jan 24, 2009 3:00 pm
Thanked: 11 times
GMAT Score:730

by BuckeyeT » Mon Oct 19, 2009 5:13 am
vkb16-

I hope this explanation helps. Let's suppose our 50% acid solution is A and our 30% solution is B.

"Some part of a 50% solution of acid was replaced with an equal amount of 30% solution of acid..." should translate to...
A - xA + xB (where x is the amount replaced)
Basically, we're replacing x amount of solution A with x amount of solution B (as the question states "equal amount").

We know that the new solution is 40%, so:
A - xA + xB = .4
Substitute back in our original values
.5 -.5x +.3x = .4
-.5x +.3x = -.1
-.2x = -.1
x = 1/2

C.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 324
Joined: Thu Dec 24, 2009 6:29 amFollowed by: 1 member
Thanked: 17 times

by rahul.s » Sat Jan 23, 2010 1:56 am
is there a way of plugging in numbers and solving it. i tried, but couldn't get it. could someone please let me know?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members
Thanked: 137 times

by thephoenix » Sat Jan 23, 2010 2:13 am
another method to solve such q is attached
Attachments
rra.doc
(24.5 KiB) Downloaded 121 times
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1