Source: Official Guide for GMAT Review 2016 Problem Solving; #55

1

Of the land owned by a farmer

Of the land owned by a farmer, 90 percent was cleared for planting. Of the cleared land, 40 percent was planted with soybeans and 50 percent of the cleared land was planted with wheat. If the remaining 720 acres of cleared land was planted with corn, how many acres did the farmer own?

2 Explanations

1

John Robertson

You're given 1 absolute quantity (720 acres for corn), so sort of solving from the bottom to the top as far as small acreage to total.

Soybean and wheat are somewhat distractors in this problem, as you could be tempted to solve for their acreage as well.

1) Starting with 720 acr for corn, you can find it's 10% of total acreage of cleared land. If 10% is 720, 100% is 7,200 (10%x10=100%, 720x10=7,200)

2) 7,200 acr is 90% of the cleared land. Using 90/100=7200/x, x=8,000. ANS D.

Feb 23, 2017 • Comment

2

ROHAN MATHEW

The 90% of the cleared land is subdivided into 3 categories. Corn being 10% [100-(40+50)}. The 90% cleared land is 720/10*100=7200 acres.[10% of the total cleared land represents corn of 720 acres]
Now 7200 acres represents 90% cleared land.So find total land(ie.100%), which is calculated as follows 7200/90*100=8000 acres..
Hope somebody finds it helpful.

Mar 2, 2016 • Comment

Cydney Seigerman, Magoosh Tutor

Thanks for sharing your solution :D

Mar 4, 2016 • Reply

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