Question

The table below shows how the cost of building a fence is related to the length of the fence.

Fence Cost
Length (meters) Cost (dollars)
20 400
30 600
40 800
50 1,000
60 1,200
Which equation correctly relates x, the length in meters, and y, the cost in dollars?

A.
y
=
20
x

B.
y
=
20
x
+
400

C.
y
=
200
x

D.
y
=
10
x
+
200

Answer 1

Find the rate: cost increases by $200 for every 10 m → $20 per meter. So y = 20x. (Check: x = 20 → y = 20·20 = 400.) Answer: A.