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 →

A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 1223
Joined: Sat Feb 15, 2020 2:23 pmFollowed by: 1 member
by BTGModeratorVI » Wed Jan 06, 2021 8:18 am

Timer

00:00

Answers

A

B

C

D

E

Stats

Difficulty—

A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%

Answer: E
Source: Manhattan prep
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: 8155
Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members
Location: Los Angeles, CA
Thanked: 43 times

Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentrat

by Scott@TargetTestPrep » Thu Jan 14, 2021 4:35 am
BTGModeratorVI wrote: ↑
Wed Jan 06, 2021 8:18 am
 A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%

Answer: E
Solution:

If a 400-milliliter solution is 20% alcohol by volume, it has 400 x 0.2 = 80 milliliters of alcohol. Thus the concentration of alcohol, when 100 milliliters of water is added, is:

80 / (400 + 100) = 80/500 = 16/100 = 16%

Alternate Solution:

To a 400 ml solution of 20% alcohol, we add 100 ml of water, which has 0% alcohol, and we obtain 500 ml of a solution with x% alcohol. Creating an equation, we have:

400 (0.20) + 100 (0) = 500x

80 + 0 = 500x

0.16 = x

Converted to a percent, we see that x = 16%.


Answer: E

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentrat

by Brent@GMATPrepNow » Thu Jan 14, 2021 7:19 am
BTGModeratorVI wrote: ↑
Wed Jan 06, 2021 8:18 am
 A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%

Answer: E
Source: Manhattan prep
A 400 milliliter solution is 20% alcohol by volume.
20% of 400 = 80
So, the original solution contains 80 milliliters of alcohol

If 100 milliliters of water is added...
400 + 100 = 500
So, our NEW solution has a total volume of 500 milliliters

...what is the new concentration of alcohol, as a percent of volume?
NEW concentration of alcohol = 80/500
Divide top and bottom of our fraction by 5 to get: 16/100, which is the same as 16%

Answer: E

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1