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Head First 2D Geometry by Dawn Griffiths, Stray

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triangle properties
Fencing costs money
To make sure that only the people who’ve bought a ticket for your
festival can come in, you’re going to need to set up a security fence
around the perimeter. And that’s not cheap! The cost of setting up
the security fence will be different for each potential venue.
$15
90m
60m
Field A
80m
85m
85m
Field B
42m
33m
33m
60m
60m
Field C
you are here 4 153
Work out what it would cost to put up a security fence around each venue.
(Fencing costs $15 per meter—work by rounding UP to a whole meter.)
Use a ca
lcul
a
t
or
because the number
s
get a bi
t ugl
y.
field C is the cheapest
154 Chapter 4
3364 +
Rounded up t
o the nex
t meter—
can’t buy a bi
t of a f
enc
e panel!
Work out what it would cost to put up a security fence around each venue. (Fencing costs $15
per meter—work by rounding UP to a whole meter.)
60m
Field A
For field A we need to use the Pythagorean
Theorem to find the missing side (the hypotenuse).
H
2
= 60
2
+ 90
2
H
2
= 3600 + 8100
H
2
= 11700
H = 11700
H = 108.16 = 109m
H
Perimeter, P = 60 + 90 + 109
P = 259m
Don’t f
orget y
our uni
ts.
Field B
80m
85m85m
Field C
42m
33m
33m
60m
60m
Perimeter, P = 80 + 85 + 85
P = 250m
Perimeter, P = 60 + 60 + 33 + 33 + 42
P = 228m
Cost = 259 x 15 = $3885
Cost = 250 x 15 = $3750
Cost = 228 x 15 = $3420
F
i
eld A is a
r
ight tr
iangle.
T
his one is the cheap
es
t.
90m

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