To calculate the area of a circle, which formula should be used?

A. A= π⋅r3

B. A= π⋅d

C. A= 2π⋅r

D. A= π⋅r2

D

Step-by-step explanation:

Area equals pie times radius squared, which makes sense in a weird way since double radius is diameter, so radius times radius is area, well that times pi

i hope this helps u :)

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step-by-step explanation:

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).