Weighted Avg and Percent

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 273
Joined: Thu Sep 08, 2011 6:50 am
Thanked: 5 times
Followed by:3 members

Weighted Avg and Percent

by fangtray » Mon Mar 12, 2012 6:00 am
A company sells only pens and pencils. The revenue from pen sales in 2007 was up 5% from 2006, but the revenue from the pencil sales declined 13% over the same period. If overall revenue was down 1% from 2006 to 2007, what was the ratio of pencil revenues to pen revenues in 2006?

This question was from a MGMAT booklet i have and there was no 5 answer choices. I wasn't sure how to use the plug in method to answer this question, so I used algebra and got the right answer.

I did the following:

1.05x + 0.87y = 99
x+y = 100

we now have 2 equations.. we can find x and y.

However, this way took me like 3 minutes. Is there a faster way?
Source: — Problem Solving |

Senior | Next Rank: 100 Posts
Posts: 92
Joined: Thu Oct 06, 2011 8:06 am
Thanked: 18 times

by Neo Anderson » Mon Mar 12, 2012 8:37 am
try using allegation!

Refer the attached figure

Image

Newbie | Next Rank: 10 Posts
Posts: 5
Joined: Sun Mar 11, 2012 2:24 am

by Snowbirds » Tue Mar 13, 2012 1:53 am
I solved by writing one equation
1.05x + .87y=.99(x+y)

.06x = .12y
x/y = .12/.06 = 2

Took me 2-3 minutes.

Neo, no clue what you did, can you describe the picture and what allegation refers to?