GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 12 Nov 2019, 16:08

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.

Close

Request Expert Reply

Confirm Cancel

An animal that dives into a pool of water is at a depth of x, in feet,

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58991
An animal that dives into a pool of water is at a depth of x, in feet,  [#permalink]

Show Tags

New post 16 Aug 2019, 01:20
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

55% (01:31) correct 45% (01:44) wrong based on 42 sessions

HideShow timer Statistics

Senior Manager
Senior Manager
User avatar
G
Joined: 29 Jun 2019
Posts: 466
Re: An animal that dives into a pool of water is at a depth of x, in feet,  [#permalink]

Show Tags

New post 16 Aug 2019, 01:32
1
After 2 seconds the animal reaches at the greatest depth which is 16 in feet.
So ,0.5 seconds latter is 2.5.
-4(2.5 -2)^2 +16=15
Option C

Posted from my mobile device
_________________
Always waiting
Yale Moderator
avatar
S
Joined: 05 May 2019
Posts: 125
GPA: 3
Re: An animal that dives into a pool of water is at a depth of x, in feet,  [#permalink]

Show Tags

New post 18 Aug 2019, 04:43
Mohammadmo wrote:
After 2 seconds the animal reaches at the greatest depth which is 16 in feet.
So ,0.5 seconds latter is 2.5.
-4(2.5 -2)^2 +16=15
Option C

Posted from my mobile device


How'd you calculate the greatest depth mate?
Did you assume?
Manager
Manager
User avatar
S
Joined: 24 Sep 2015
Posts: 57
Location: Spain
Concentration: Strategy, Entrepreneurship
GPA: 3.9
WE: Management Consulting (Consulting)
CAT Tests
An animal that dives into a pool of water is at a depth of x, in feet,  [#permalink]

Show Tags

New post 18 Aug 2019, 07:16
There are two ways of doing this problem. The first one is for people who still remembers what derivatives are and the second one is applying logic to know after how many seconds the animal reaches the geatest depth

1º DERIVATIVES

Engineers taking the GMAT will still remember that to calculate the max/min value of a function f(x) you must equal to zero the derivative of f(x) (denoted by f'(x))

derivate of f(x) = −4(t−2)^2+16 ---> f'(x) = -4*2(t-2) = 0 ---> t = 2 (this means that after 2 seconds the animal reached the highest depth)

so we need to substitute t = 2 + 0.5 in the original equation to know the depth of the animal 0.5 seconds after reaching the greatest depth

x = −4(t−2)^2+16 ---> x = -4(2.5-2)^2+16 ---> x = -4(0.5)^2+16 ---> x = -1+16 ---> x = 15

OPTION C

2º CALULATING t WHEN REACHING GREATEST DEPTH

The equation is x = −4(t−2)^2+16 and we need to make x the highest possible. When would it be the highest taking into account that one term is adding up (+16) and one term deducting (−4(t−2)^2)?. The answer is when the deducting element is zero so that x is max. The deducting term is zero when t = 2

Therefore, we need to calculate x when t is 2 + 0.5 = 2.5 seconds

Again solution is x = 15

OPTION C
_________________
One way to keep momentum going is to have constantly greater goals - Michael Korda

Kudos me if this post helps you ;)
SVP
SVP
User avatar
P
Joined: 03 Jun 2019
Posts: 1836
Location: India
Premium Member Reviews Badge CAT Tests
An animal that dives into a pool of water is at a depth of x, in feet,  [#permalink]

Show Tags

New post 18 Aug 2019, 07:38
Bunuel wrote:
An animal that dives into a pool of water is at a depth of x, in feet, after t seconds, where \(x = - 4(t - 2)^2 + 16\). At what depth, in feet, is the animal 0.5 seconds after it reaches its greatest depth?

A. 7
B. 12
C. 15
D. 16
E. 17


Given: An animal that dives into a pool of water is at a depth of x, in feet, after t seconds, where \(x = - 4(t - 2)^2 + 16\).

Asked: At what depth, in feet, is the animal 0.5 seconds after it reaches its greatest depth?

An animal that dives into a pool of water is at a depth of x, in feet, after t seconds, where \(x = - 4(t - 2)^2 + 16\).
x is max when t=2 deepest depth x = 16

At what depth, in feet, is the animal 0.5 seconds after it reaches its greatest depth
At t = 2+.5 =2.5
\(x= -4(.5)^2 +16 = 16 - 4*.25 = 16 -1 = 15\)

IMO C
_________________
"Success is not final; failure is not fatal: It is the courage to continue that counts."

Please provide kudos if you like my post. Kudos encourage active discussions.

My GMAT Resources: -

Efficient Learning
All you need to know about GMAT quant

Tele: +91-11-40396815
Mobile : +91-9910661622
E-mail : kinshook.chaturvedi@gmail.com
Intern
Intern
avatar
B
Joined: 15 Aug 2018
Posts: 11
Re: An animal that dives into a pool of water is at a depth of x, in feet,  [#permalink]

Show Tags

New post 18 Aug 2019, 07:48
sharathnair14 wrote:
Mohammadmo wrote:
After 2 seconds the animal reaches at the greatest depth which is 16 in feet.
So ,0.5 seconds latter is 2.5.
-4(2.5 -2)^2 +16=15
Option C

Posted from my mobile device


How'd you calculate the greatest depth mate?
Did you assume?


Read the equation again it is -4(t -2)^2 +16 …… the highest depth can be 16 when t = 2.
GMAT Club Bot
Re: An animal that dives into a pool of water is at a depth of x, in feet,   [#permalink] 18 Aug 2019, 07:48
Display posts from previous: Sort by

An animal that dives into a pool of water is at a depth of x, in feet,

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





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