MBA Spotlight Virtual MBA Fair is Oct 13 – 21. Learn how to Register and Attend – it’s Free! New to GMAT Club? Watch this Video
close

It is currently 28 Sep 2020, 15:26
Register
GMAT Club Tests
Decision Tracker
My Rewards
New comers' posts
New posts
Unanswered

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Go to My Error Log Learn more
Close

Request Expert Reply

Confirm Cancel
PREVIOUS TOPIC
NEXT TOPIC
According to a certain estimate, the depth N(t), in centimeters, of
22 posts Go to First Unread Post
Print view
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
SORT BY:
Date
Kudos
   1   2 
Tags :
Find Similar Topics 

Show Tags
Hide Tags

avatar
B
Paridhi18
Intern
Intern
Joined: 23 Jun 2020
Posts: 6
Re: According to a certain estimate, the depth N(t), in centimeters, of [#permalink] New post  25 Aug 2020, 00:56
Bunuel wrote:
Baten80 wrote:
puneetkr wrote:
the expression is N(t)= -20(t-5)^²+500
(of course valid after 2:00 in the morning)

"the depth would be maximum" means the value of the above expression should be maximum
or the value of square term (which has a negative 20 attached to it) should be minimum i.e. zero

the square part is zero at t=5

so the time at which the depth is maximum is 2:00 + 5 hrs= 7:00 (B)



if -20(t-5)^²=0
then t = 5
But Why is the 500 of the equation is not considered? Show your complete calculation.


According to a certain estimate, the depth N(t), in centimeters, of the water in a certain tank at t hours past 2:00 in the morning is given by N(t)= -20(t-5)^²+500 for 0≤t≤10. According to this estimate, at what time in the morning does the depth of the water in the tank reach its maximum?

A. 5:30
B. 7:00
C. 7:30
D. 8:00
E. 9:00

Consider this: \(-20(t-5)^2\leq{0}\) hence \(500-20(t-5)^2\) reaches its maximum when \(-20(t-5)^2=0\), thus when \(t=5\). 2:00AM+5 hours=7:00AM.

Answer: B.

Hope it helps.


Hi Bunuel, how did we deduce \(-20(t-5)^2\leq{0}\)?

Thanks,
User avatar
V
MathRevolution
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 9710
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: According to a certain estimate, the depth N(t), in centimeters, of [#permalink] New post  25 Aug 2020, 03:24
1
Expert Reply
N(t)= -20\((t - 5)^2\) + 500

For this to be maximum, we need -20\((t - 5)^2\) minimum (zero) and that will happen when t = 5.

Hence, after 5 hours from 2:00 a.m. i.e., 7 a.m.

Answer B
_________________
MathRevolution: The World's Most "Complete" GMAT Math Course!
Score an excellent Q49-51 just like 70% of our students.
[Free] Full on-demand course (7 days) - 100 hours of video lessons, 490 lesson topics, and 2,000 questions.
[Course] Starting $69 for on-demand and $60 for tutoring per hour.
Signature Read More
GMAT Club Bot
gmatclubot
[#permalink]
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
   1   2 
Moderators:
chetan2u
Math Expert
8853 posts
Bunuel
Math Expert
67040 posts
VeritasKarishma
Veritas Prep GMAT Instructor
11019 posts
yashikaaggarwal
Senior Moderator - Masters Forum
2026 posts
generis
Senior SC Moderator
4155 posts
Feedback

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions