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 →

Prep question

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 5
Joined: Sun Jan 10, 2010 5:46 pm
by hnature0704 » Tue Nov 09, 2010 2:55 am
Please help! Thank you :) (From Powerprep)

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is incresed by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

a) 100% decrease
b) 50% decrease
c) 40% decrease
d) 40 % increase
e) 50% increase
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 1179
Joined: Sun Apr 11, 2010 9:07 pmFollowed by: 88 members
Location: Milpitas, CA
Thanked: 447 times

by Rahul@gurome » Tue Nov 09, 2010 3:09 am
Let r be the rate of the chemical reaction.
Then r = kA^2 / B, where k is any constant.
When the concentration of chemical B is incresed by 100 percent, let the new concentration of A = A1 and that of B = B1
Then kA^2 / B = kA1^2 / B1
Now chemical B is incresed by 100% means B1 = 2B
kA^2 / B = kA1^2 / 2B
A^2 = A1^2 / 2
2(A^2) = A1 ^ 2
A1 = A√2
A1 = 1.4A implies A1 = A + 0.4 A, which is 40% increase.
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 437
Joined: Sat Nov 22, 2008 5:06 amFollowed by: 1 member
Location: India
Thanked: 50 times
GMAT Score:580

by beat_gmat_09 » Tue Nov 09, 2010 3:12 am
hnature0704 wrote:Please help! Thank you :) (From Powerprep)

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is incresed by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

a) 100% decrease
b) 50% decrease
c) 40% decrease
d) 40 % increase
e) 50% increase
R = k (Ca)^2/(Cb)
Can-new Ca
Cb increased by 100% i.e. Cb is doubled.
New R = k (Can) ^2/2Cb = k (Ca) ^2/Cb
cancel out Cb.
Can ^2 = 2. Ca ^2
Take square root of both sides.
(New Ca)Can = (2)^(1/2) Ca
(2)^1/2 is = 1.41
Therefore % increase in Concentration of chemical A = 40%
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1