Area of non paved area

This topic has expert replies
Legendary Member
Posts: 518
Joined: Tue May 12, 2015 8:25 pm
Thanked: 10 times

Area of non paved area

by nikhilgmat31 » Thu Jun 04, 2015 12:49 am
What is the cost to plant grass in the non-paved area of the rectangular lawn of 60 meter length and 30 meter width, if it costs $2/m2 to plant the grass? Note that the pavement has a uniform width of 5 meters.

refer to image
Attachments
yard.JPG
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pm
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:511 members
GMAT Score:800

by [email protected] » Thu Jun 04, 2015 9:43 am
Hi nikhilgmat31,

What is the source of this question? I ask because we're forced to estimate some of the measurements based on the drawing (and the GMAT would NOT expect you to do that). If there were 5 answer choices, we might be able to eliminate certain options as being too big or too small, but we don't have those to work with either.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Thu Jun 04, 2015 10:33 am
Deleted (after reading Ian's post :-))

Cheers,
Brent
Last edited by Brent@GMATPrepNow on Thu Jun 04, 2015 11:29 am, edited 1 time in total.
Brent Hanneson - Creator of GMATPrepNow.com
Image

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2623
Joined: Mon Jun 02, 2008 3:17 am
Location: Montreal
Thanked: 1090 times
Followed by:355 members
GMAT Score:780

by Ian Stewart » Thu Jun 04, 2015 10:51 am
Brent@GMATPrepNow wrote: That's not entirely true.

If we take the HORIZONTAL pieces and stick them together, we get a strip of pavement that's 60 meters long and 5 meters wide.
So, the TOTAL area of this strip = (60)(5) = 300 square meters.
[email protected] wrote: I ask because we're forced to estimate some of the measurements
I disagree with both of you. :)

We only need one measurement here, but we do need it. From the diagram, the paving does not extend all the way from the left end of the lawn to the right end. We need to know just how far it extends horizontally. So we need one measurement, but only one. You can see that this is the case just by imagining shrinking or extending the horizontal red band in the middle of the lawn (moving the top right vertical portion at the same time). By doing that, the total red area will clearly shrink or grow, since the area of the middle horizontal band will change while the remaining red area will remain unchanged.

If you chop up the red rectangle appropriately, you can piece together vertical strips to get a rectangle of paving that extends from the bottom to the top, so with area 150. The remaining horizontal pieces can then fit together to make a rectangle with a width of 5, and a length which appears to be about 40 or 45 in the picture. So I'd expect the area of the paving to be roughly 375, and the area of the lawn to be roughly 1800 - 375 = 1425, and the cost to be (2)(1425) = 2850. But that's based on an estimate of the horizontal length of the bottom strip. It would be easier to display how to chop up the picture with a diagram, but hopefully it's clear.

Since this was posted in the DS section, I wonder if it's meant to be a DS question. If so, the info we're really looking for is any information that tells us how far the paving extends horizontally across the lawn. We don't care about any vertical distances, besides the 30 meters given in the question.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Thu Jun 04, 2015 11:31 am
Ha - good catch, Ian!!!

I never noticed that the path doesn't extend all the way to the far right side.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image