Question

Anyone ready for a math question?

Answer 1

@marissalovescats

Answer 2

Okay so the equation for the Surface Area is:

4(pi)(r^2)

So here in this picture the diameter is 50

So that makes the radius what?

Answer 3

25?

Answer 4

Exactly!

So:

SA=4(pi)(25^2)

Also notice this answer is not in terms of pi so that means you will have to multiple whatever you get for 4(25^2) by pi

Answer 5

4/3(pi)(25^2) = 2500/3(pi)

Answer 6

No that is the Volume of a Sphere equation.

Surface are is just: 4(pi)(r^2)

There is not 4/3

Answer 7

When is it the right time to do 4/3 and just 4?

Answer 8

\[SA = 4 \pi r^2 ~~~~~ r = \frac{ d }{ 2 }\]

Answer 9

2500 (pi)

Answer 10

@iambatman Thank you we covered that I've been helping him for a couple questions now

Answer 11

4/3 is involved with finding the Volume of a sphere.

And yes but remember what I said, the answers here don't have pi in it so that means you need to multiply 2500 by pi

Answer 12

So what do you get? (you'll have to round it to the nearest whole number)

Answer 13

What I did was 4(pi)(25^2) = 2500 cm^2

Answer 14

Yes but 25^2(4) = 2500 and then you still have the pi

So yes it is 2500pi

But remember pi is a number do 3.14....it repats

So in order to get the answer you have to multiple 2500 by your pi button on the calculator.

You know you have to multiply it by pi because there is no pi in any of the answers so this means they want a full number answer.

Answer 15

So what is 2500 times pi?

Answer 16

2500 pie's

Answer 17

thats a lot of pies

Answer 18

I know ew.

I mean I bake pies, I bake a lot. I just don't really like pie.

Answer 19

I'm the classic baking cat lady. Hi.

Answer 20

Oh you meant, I have to multiply 2500 by 3.14 = 7850

Answer 21

Okay but you multiplied it by 3.14 and 3.14 is just a rounding of pi.

You have to hit your pi button.

And when you do you actually get 7853.98 which rounds to 7854

Answer 22

HOld on, let me check.

Answer 23

Sorry, I have my calculator on degree mode.

Answer 24

It's important to hit your actual pi button and not just multiplying it by 3.14 because you get further from the actual real answer because you're missing a lot of digits because pi is never ending.

Answer 25

had*

Answer 26

So on your calculator just do:

2500 *hit times button* *hit pi button* *hit enter*

And you should come out to 7853.981634

Answer 27

Yes I did that but I had it on degree mode and I got 2500

Answer 28

It does not matter what mode you are in, you still get the same answer. I just did it both ways.

Answer 29

But either way, the Surface Area is 7854 cm^2

Answer 30

Just for funsies, in calculus you can say that an infinitesimal change of the radius changes the volume by an infinitesimal amount, and that extra little "egg shell" of volume is the surface area. \[\frac{d}{dx}(\frac{4}{3} \pi r^3) = 4\pi r^2\]

Answer 31

Not on my calculator.

Answer 32

Well either way, we got the answer

Answer 33

But either way.

Answer 34

And yes @Kainui I sees how that is with using the calculus

Answer 35

Can't find the derivative button on my calculator either. What is this nonsense @Kainui

Answer 36

No but you can take an integral :D

Answer 37

I'm getting a pink TI 84+ Silver Edition with colored screen for me 18th birthday coming up.. Probably too excited about it. I already named her, but don't have her yet.

Answer 38

I took an integral one time. Felt super guilty, so I returned it.

Answer 39

LOL