Head First 2D Geometry

factoring in perimeter

250 Chapter 6

Calculate the perimeters of the two lawns. How does this account

for the difference in time spent on each lawn? What do you think

Edward should do?

Same shape, different perimeters

Your friends ran into a similar problem back in Chapter 4 when they

were picking out a venue for the rock festival—the biggest field didn’t

necessarily have the most perimeter. For our lawn calculations, even if we

know the area of a particular lawn, we can’t make any assumptions about

its perimeter or how long it will take to edge the lawn. And currently,

Edward’s charges are only based on lawn area.

Same Area ≠ Same Perimeter

45 meters

16 meters

34 meters

Parallelogram perimeter = 45 + 34 + 45 + 34

= 158 meters

36 meters

20 meters

Rectangle perimeter = 36 + 20 + 36 + 20

= 112 meters

It takes longer to maintain the parallelogram lawn because the perimeter is so much greater

and therefore takes longer to edge. Edward’s charges need to change so that lawn perimeter is

considered, too.

you are here 4 251

quadrilaterals

 A parallelogram is a four-sided shape

whose opposite sides are parallel to

each other.

Opposite sides of a parallelogram 

are congruent.

Opposite angles of a parallelogram 

are congruent.

Consecutive angles of a 

parallelogram are supplementary.

To calculate ...