Head First 2D Geometry

so far the square is winning

Work the formula for circle area backward to get the butt count

for the circle shaped hot tub.

circle area = ∏r

2

perimeter = 2

∏r

Butts = perimeter

6 =

∏r

2

∏ 3.1415

6 = 6

0.5

0.5 = 17.3 butts

P = 2 x 3.1415 x 1.38

P = 8.67m

Butts = 8.67

= r

2

1.9m

2

= r

2

1.38m = r

radius

6m

2

Circumf

er

ence in the

case of a circle

T

ha

t’s m f

or meter

s, not a new var

iable!

Or 17.4 butts if y

ou didn’t round

as y

ou w

orked—ei

ther is OK.

The square tub beats the circle tub

So, when it comes to providing butt-space for a 3 cubic

meter volume of water, the square shaped hot tub is better

than the circle shaped one.

Both tubs have the same area.

17.3 butts

19.6 butts

Both tubs are the same depth.

288 Chapter 7