Question

The number of pepperoni slices that kim puts on a pizza varies directly as the square of the diameter of the pizza. If she puts 15 slices on a 10" diameter pizza, how many slices should she put on a 16" diameter pizza?

Answer 1

varies directly as the square of the diameter
square means to multiply by itself or x^2
that means
k=x/y
in this case
x=15
y=10^2
k=15/10^2=15/100=3/20
so the new pizza is
k=x/16^2
k=3/20
3/20=x/16^2
evaluate 16^2
3/20=x/256
multiply both sides by 256
768/20=x
384/10=x
38.4=x
she should put about 38 slises

Answer 2

You can make this into a fraction, and then simplify it.

15/10, right?

15/10 = 3/2

Then compare 3/2 to the rest of the equation

3/2 = x/16

2 * 8 = 16
so
3 * 8 = x
x = 24

Kim would put x number of pizza slices on her pizza.
So she would be putting on 24 slices on her pizza.