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 →

The speed of a subway train is represented by the equation..

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Moderator
Posts: 2644
Joined: Sun Oct 29, 2017 2:08 pmFollowed by: 2 members
by AAPL » Sun Feb 25, 2018 10:29 am
The speed of a subway train is represented by the equation z=s^2+2s for all situations where 0 ≤ s ≤ 7, where z is the rate of speed in kilometers per hour and s is the time in seconds from the moment the train starts moving. In kilometers per hour, how much faster is the subway train moving after 7 seconds than it was moving after 3 seconds?

A. 4
B. 9
C. 15
D. 48
E. 63

The OA is D.

I don't have clear this PS question.

I just need to evaluate the speed equation for z(7) and z(3) and then find the difference between them? I appreciate if any expert explains it to me. Thank you so much.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 2663
Joined: Wed Jan 14, 2015 8:25 amFollowed by: 128 members
Location: Boston, MA
Thanked: 1153 times
GMAT Score:770

by DavidG@VeritasPrep » Sun Feb 25, 2018 11:44 am
AAPL wrote:The speed of a subway train is represented by the equation z=s^2+2s for all situations where 0 ≤ s ≤ 7, where z is the rate of speed in kilometers per hour and s is the time in seconds from the moment the train starts moving. In kilometers per hour, how much faster is the subway train moving after 7 seconds than it was moving after 3 seconds?

A. 4
B. 9
C. 15
D. 48
E. 63

The OA is D.

I don't have clear this PS question.

I just need to evaluate the speed equation for z(7) and z(3) and then find the difference between them? I appreciate if any expert explains it to me. Thank you so much.
You're exactly right.

Her speed at 7 seconds: 7^2 + 2*7 = 49 + 14 = . 63
Her speed at 3 seconds: 3^2 + 2*3 = 9 + 6 = 15
The difference 63-16 = 48. The answer is D
Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course
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 » Mon Jun 10, 2019 6:29 pm
AAPL wrote:The speed of a subway train is represented by the equation z=s^2+2s for all situations where 0 ≤ s ≤ 7, where z is the rate of speed in kilometers per hour and s is the time in seconds from the moment the train starts moving. In kilometers per hour, how much faster is the subway train moving after 7 seconds than it was moving after 3 seconds?

A. 4
B. 9
C. 15
D. 48
E. 63

.
z(7) = 7^2 + 2(7) = 49 + 14 = 63

z(3) = 3^2 + 2(3) = 9 + 6 = 15

So the difference is 63 - 15 = 48.

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