Trapezoid problem

May 2010
13
0
Lot 21 is a trapezoid with the two bases perpendicular to the road. The scale drawing below uses 1/2 inch = 40 ft.



A) 1/2 acre
B) 2 acres
C) 2 1/2 acres
D) 3 acres

So here's how I try to solve it:

A = 1/2 x 4 (5 + 3 1/2)
A = 1/2 x 20 x 8 1/2
A= 85

What am I doing wrong? What steps do I take?
 

galactus

MHF Hall of Honor
Jul 2006
3,002
1,124
Chaneysville, PA
Did you use your scale that 1/4 inch equals 40 feet?.

b1: How many 1/2 inches are in 3.5 inches?. 7

7*40=280

b2: How many half inches are in 5 inches?. 10

10*40=400

Proceed in that fashion and you should be OK. It's like that other problem I stepped through involving scales.

Find the square feet form this and then divide by 43,560 to find the acres.
 
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galactus

MHF Hall of Honor
Jul 2006
3,002
1,124
Chaneysville, PA
In real-life, scales on blueprints are usually given as 1" = however many feet.

If 1/2 inch is 40 feet, then 1 inch is 80 feet. So, 5 inches would be 400 feet.

You could proceed this way.