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

Redeem

picking numbers and variable choices

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Thu Apr 23, 2009 4:42 am
Location: paris

picking numbers and variable choices

by martinho » Mon Apr 27, 2009 11:57 pm
Hello,
I don't understand how to solve this problem:
Each writer of the local newspaper is paid as follows: a dollars for each of the first n stories each month, and a+b for each story thereafter, where a>b.
How many more dollars will a writer who submits n+a stories in a month earn than a writer who submits n+b stories?

A.(a+b)(a+b+n)
B.a-b
C.a2-b2
D.n(a-b)
E.an+bn-an


I've got the answer but not the explanation.
I really need to develop my ability to put words into equations but that's still difficult for me.
This question is rated as advanced by Kaplan.

Cheers!
Top
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 682
Joined: Fri Jan 16, 2009 2:40 am
Thanked: 32 times
Followed by:1 members

Re: picking numbers and variable choices

by Vemuri » Tue Apr 28, 2009 12:42 am
Answer should be C.

For these type of questions, plugging in values will be the easiest & fastest way of solving.

Lets assume a=$10, b=$5, n=5 stories

For (n+a)=15 stories, the dollars earned is $10+10*$15=$160
For (n+b)=10 stories, the dollars earned is $10+5*$15=$85
Difference = $160 - $85 = $75

Now, input these variable values in the answer choices & observe only C equals $75.

Hope this helps.
Top
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Thu Apr 23, 2009 4:42 am
Location: paris

by martinho » Tue Apr 28, 2009 1:03 am
Cheers mate!
I've figured out that I often look for difficulty into questions.
That's weird.
I may have done it because of kaplan's book: you can see the difficulty level in the margin...
Thanks again
:D
Top
Master | Next Rank: 500 Posts
Posts: 148
Joined: Wed Dec 10, 2008 5:13 pm
Location: SF, CA
Thanked: 12 times

by lilu » Thu Apr 30, 2009 9:17 am
Or you can actually translate word into equations:
an per story
a+b per additional story
Now, for the first writer:
na+(n+a)(n+b)=2an+bn+a^2+ab

For the second writer:
na+(n+b)(a+b)=2an+ab+b^2+bn

Now, we need to find the difference and we know that a>b, so subtract second expression from first and you' ll get a^2-b^2
And that's your answer
The more you look, the more you see.
Top
Post new topic Post Reply
• Page 1 of 1