We know that gold density is 19.3 g/cm^3 and that the price per gram of gold is $55.62. With this we want to solve different problems
The answers are:
24) f(x) = $55.62*x
25) g(x) = (19.3 g/cm^3)*x^3
26) The domain is x > 0cm
27) The price is $8,587.73
24) We know the price per gram of gold, then if we have x grams, the price will be x times the price per gram, then we can write the function as:
f(x) = $55.62*x
25) A cube of sidelength x has a volume equal to:
v = x^3
The mass is equal to the density times the volume, then we can write:
g(x) = (19.3 g/cm^3)*x^3
26) g(x) gives the mass of a cube of gold.
f(x) gives the price of a piece of gold of a given mass.
Then the composition f(g(x)) works correctly.
The domain is given for the possible values of x (the side length of the cube) so we only can say that x must be larger than zero, then the domain is:
x < 0cm
27) Here we just use the composition f(g(x)) with x = 20cm
f( g(20cm)) = ($55.62)*(19.3 g/cm^3)*(20cm)^3 = $8,587.73
The value of that cube is $8,587.73
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