The surface area of a cone with radius r units and slant height s units is shown below: surface area = 3.14(rs + r2) part a: if r = 3 units and s = 5 units, write an expression that can be used to calculate the surface area of the cone. (4 points) part b: what is the surface area of the cone? show your work. (6 points)

Answers:
Part A: 3.14((3)(5) + ) 
Part B: 75.36 units^2

Explanations:
Part A: This is simple substitution. 
First, replace both r variables with the value you are given; r = 3. 
3.14(rs + )
3.14((3)s + ) 
Now replace the s variable with the value you are given; s = 5. 
3.14((3)s + )  
3.14((3)(5) + ) 

Part B: Now all you have to do is solve this problem. 
3.14((3)(5) + ) 
Make sure you use PEMDAS, so deal inside the parentheses first. 
You can deal with the exponent:
3.14((3)(5) + ) = 3.14((3)(5) + 9) 
Now multiply 3 • 5 
3.14((3)(5) + 9) = 3.14(15 + 9) 
Keep looking inside the parentheses.
3.14(15 + 9) = 3.14(24)
Now multiply:
3.14(24) = 75.36 units^2  (it is squared because area or surface area is squared, just like volume is cubed.)