PR 1024 Functions #6

BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

This topic has expert replies

Post new topic Post Reply

Previous Topic Next Topic

CR: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu Mar 15, 2012 11:21 am

PR 1024 Functions #6

by CR » Wed Apr 11, 2012 8:47 am

Hi all,

Wondering if someone can help me understand this, its the first Q in this book to stump me..
Page 164
https://books.google.ca/books?id=-9wUwAT ... e&q&f=true is the digital free look at the Q

f(x) = x^2 + x
f(y) = ?
(1) $y = 3(($10)+30)
(2) $y = $($(4))

Answer is apparently D both sufficient though when looking at the solution it makes absolutely no sense to me... (soln on page 211)

I am convinced this is a book error unless someone can explain why it isnt.

Thanks!!

Quote

Source: Beat The GMAT — Data Sufficiency | Wed Apr 11, 2012 8:47 am

Shalabh's Quants: Master | Next Rank: 500 Posts; Posts: 134; Joined: Fri Apr 06, 2012 3:11 am; Thanked: 35 times; Followed by:5 members

by Shalabh's Quants » Thu Apr 12, 2012 12:04 am

CR wrote:Hi all,

Wondering if someone can help me understand this, its the first Q in this book to stump me..
Page 164
https://books.google.ca/books?id=-9wUwAT ... e&q&f=true is the digital free look at the Q

f(x) = x^2 + x
f(y) = ?
(1) $y = 3(($10)+30)
(2) $y = $($(4))

Answer is apparently D both sufficient though when looking at the solution it makes absolutely no sense to me... (soln on page 211)

I am convinced this is a book error unless someone can explain why it isnt.

Thanks!!

can you pl. put down the question?

Shalabh Jain,
e-GMAT Instructor

Quote

CR: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu Mar 15, 2012 11:21 am

by CR » Thu Apr 12, 2012 5:20 am

put down the question? You want me to remove the link?

The question and link to the Q are in the post..

Quote

Shalabh's Quants: Master | Next Rank: 500 Posts; Posts: 134; Joined: Fri Apr 06, 2012 3:11 am; Thanked: 35 times; Followed by:5 members

by Shalabh's Quants » Thu Apr 12, 2012 6:40 am

CR wrote:put down the question? You want me to remove the link?

The question and link to the Q are in the post..

No.I mean can you pl. post the question? I cannot access the question via link. I will surely help dear!

Shalabh Jain,
e-GMAT Instructor

Quote

CR: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu Mar 15, 2012 11:21 am

by CR » Thu Apr 12, 2012 8:46 am

The question is in the first post

Its a Data Sufficiency Q, it literally reads as:
F at x = x squared plus x
what is F at y?

f(x) = x^2 + x
f(y) = ?

Scenario 1: weird dollar symbol y = 3 multiplied by ( ( weird dollar symbol 10) plus 30)
Scenario 2: weird dollar symbol y = weird dollar symbol multiplied by ( ( weird dollar symbol multiplied by 4))
(1) $y = 3(($10)+30)
(2) $y = $($(4))

The scenarios don't even follow the same function at x pattern... very odd.

Quote

Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pm; Location: Toronto; Thanked: 1710 times; Followed by:614 members; GMAT Score:800

by Stuart@KaplanGMAT » Thu Apr 12, 2012 10:01 am

Hi!

The question makes no sense as you've posted it. Unfortunately, p164 is omitted from that preview of the book, so there's no way to check the actual question.

Here's how the question likely reads in order for (D) to be correct:

If f(x) = x^2 + x for all values of x, what's f(y)?

(1) f(y) = 3(f(10) + 30)
(2) f(y) = f(f(4))

We know that f(x) = x^2 + x for all values of x, accordingly, we know that:

f(y) = y^2 + y

To solve, therefore, we need a value for y or a way to solve for f(y) directly.

(1) f(y) = some ugly equation we can turn into a number (using the function provided) - sufficient.
(2) f(y) = a double application of the function with a number provided, so we can solve - sufficient.

Accordingly, each statement is sufficient alone - choose (D).