If a tennis ball has a diameter of approximately 6.9 centimeters, what is its surface area

Question

anonymous · Answer

do you know the formula for surface area of a sphere? (ball)

anonymous · Answer

I sure dont

anonymous · Answer

why not?

anonymous · Answer

Because I dont? thats why I want help ?

anonymous · Answer

kidding... here's the sufrace area formula:
$$\large SA = 4 \times \pi \times r^2$$

anonymous · Answer

since your diameter is 6.9, take half of that to get your radius....
sorry gotta go... :(

anonymous · Answer

bye

anonymous · Answer

Dpainc is right. Just use that formula.|dw:1338507528873:dw|

anonymous · Answer

$$\text{Surface area} = 4*\pi*r^2$$
And of course, if you're given the diameter instead, it's easy to find the radius from that.

anonymous · Answer

Yeahhh about that ... Im not to good in math so can you dumb it down a little more like go step by step with me please ? :)

anonymous · Answer

Step 1, figure out what the radius is. Usually it will be given to you. If they give you the diameter, the radius is always half of the diameter.
Step 2, square the radius
Step 3, multiply that by 4
step 5, multiply that by pi

anonymous · Answer

23.3 ?

anonymous · Answer

jk that isnt even an option on this test

anonymous · Answer

those are the choices they give me 
149.57 square centimeters 

 1,032.04 square centimeters 

 299.14 square centimeters 

 598.28 square centimeters

anonymous · Answer

Is that a guess or did you try?

anonymous · Answer

I actually tried :/

anonymous · Answer

Okay, step by step then. What did you get as the radius?

anonymous · Answer

3.45

anonymous · Answer

Good. Show me the second step.

anonymous · Answer

149.57 thats the answer !

anonymous · Answer

Haha what did you do wrong the first time?

anonymous · Answer

I took the square root instead of just squaring it

anonymous · Answer

Oooooh =D

anonymous · Answer

Yes but I still need your help so dont leave ! lol

anonymous · Answer

If the smaller cylinder has a lateral area of approximately 113 square meters, what is the approximate lateral area of the larger cylinder
The bigger cylinder is 21m
an the smaller one is 9m

anonymous · Answer

Okay, well this problem has a few steps, but we're really only going to use 2 facts
1) Lateral surface area = pi*diameter*height
2) Similar shapes have corresponding parts that are proportional.

Here's the picture we have
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