Question

Just need a check

The amount a car dealership earns for selling a car is directly proportional to the price of the car. The table shows this relationship.



What is the constant of proportionality?


Car price ($) (x) 20,000 30,000 40,000
Amount earned ($) (y) 1000 1500 2000

my answer :14.5

right or wrong

Answer 1

Wrong.
If it's a matter of directly proportional, then all you need is one single point.

Look at the first one:

x = 20,000
y = 1,000

y/x = 1,000/20,000 = 0.05

y = 0.05 x

The constant of proportionality is 0.05 (5 percent).

Look at the other points just to check it out and see if it holds water:

x = 1,500
y = 30,000
x/y = 0.05 yes !

x = 2,000
y = 40,000
x/y = 0.05 yes !

It checks out.
The constant of proportionality is 5% for all points in this table.