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 →

In Dewey Elementary School, there are two second-grade

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Moderator
Posts: 2550
Joined: Sun Oct 15, 2017 1:50 pmFollowed by: 6 members
by BTGmoderatorLU » Fri May 24, 2019 2:59 pm

Timer

00:00

Answers

A

B

C

D

E

Stats

Difficulty—

Source: Magoosh

In Dewey Elementary School, there are two second-grade classes: class A has 35 students and class B has 45 students. If 40% of the students in class A walk to school, and 80% of the students in class B walk to school, what percent of all the students in the second-grade at Dewey Elementary walk to school?

A. 40%
B. 42.5%
C. 60%
D. 62.5%
E. 75%

The OA is D
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: 2095
Joined: Tue Dec 04, 2012 3:22 pmFollowed by: 247 members
Thanked: 1443 times

edit

by ceilidh.erickson » Sat May 25, 2019 10:43 am
In Dewey Elementary School, there are two second-grade classes: class A has 35 students and class B has 45 students. If 40% of the students in class A walk to school, and 80% of the students in class B walk to school, what percent of all the students in the second-grade at Dewey Elementary walk to school?

In class A, 40% (or 2/5) of the 35 students walk to school:
$$\frac{2}{5}\left(35\right)=14$$

In class B, 80% (or 4/5) of the 45 students walk to school:
$$\frac{4}{5}\left(45\right)=36$$

The total number of 2nd graders walking to school:
14 + 36 = 50

The total number of students:
35 + 45 = 80

50 as a percent of 80:
50/80 = 0.625

The answer is D.
Last edited by ceilidh.erickson on Sat May 25, 2019 11:03 am, edited 1 time in total.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2095
Joined: Tue Dec 04, 2012 3:22 pmFollowed by: 247 members
Thanked: 1443 times

by ceilidh.erickson » Sat May 25, 2019 10:56 am
Alternatively, you could treat this as a WEIGHTED AVERAGE problem.

If one class had 40% walk-to-schoolers and the other had 80%, the weighted average of both classes must be between 40 and 80. Eliminate A.

If we had an equal number of students in each class, we'd end up exactly halfway between 40 and 80: 60%. Since we have more students in class B, though, the average must be weighted toward 80% rather than 40%. That means the weighted average will be greater than 60. Eliminate B and C.

At this point, you could probably reason that since 45 is not that much greater than 35, the right answer shouldn't be that much greater than 60%. An answer of 75% would be very heavily weighted toward 80% - that's what we'd get if we had many times more students in class B than class A. So you should feel comfortable picking D as the only reasonable answer.

If you want to prove the answer mathematically (though I don't recommend that you take the time to do so on test day), you can do so as follows:

The ratio of 35 to 45 can be reduced to 7 to 9. So, we're looking for an answer that is 9/16 of the distance from 40 to 80:
$$\frac{9}{16}=\frac{x}{40}$$
$$\frac{9\cdot40}{16}=x$$
$$\frac{9\cdot5}{2}=x$$
$$\frac{45}{2}=x$$
$$22.5=x$$
$$40+22.5=62.5$$

Again, I definitely don't recommend doing this math! It's unnecessarily messy. It would be enough to realize that 9/16 is going to be just a little over the halfway point, so we want an answer that's just a little over 60%.

The answer is D.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2095
Joined: Tue Dec 04, 2012 3:22 pmFollowed by: 247 members
Thanked: 1443 times

by ceilidh.erickson » Sat May 25, 2019 11:02 am
For more on estimating to find right answers on weighted average questions, see:
https://www.beatthegmat.com/mixture-pro ... tml#796297
https://www.beatthegmat.com/mgmat-5th-e ... tml#789804
https://www.manhattanprep.com/gmat/blog ... -pen-down/

And for more on using RATIOS to solve weighted averages:
https://www.beatthegmat.com/solution-x- ... tml#818927
https://www.beatthegmat.com/at-a-certai ... tml#825832
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8151
Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members
Location: Los Angeles, CA
Thanked: 43 times

by Scott@TargetTestPrep » Tue May 28, 2019 4:44 pm
BTGmoderatorLU wrote:Source: Magoosh

In Dewey Elementary School, there are two second-grade classes: class A has 35 students and class B has 45 students. If 40% of the students in class A walk to school, and 80% of the students in class B walk to school, what percent of all the students in the second-grade at Dewey Elementary walk to school?

A. 40%
B. 42.5%
C. 60%
D. 62.5%
E. 75%

The OA is D
(35 x 0.4 + 45 x 0.8)/(35 + 45) x 100 = 50/80 x 100 = 62.5 percent

Answer: D

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
Post new topic Post Reply
• Page 1 of 1