[Math10] What I learned this week (Oct 14)

Today I will teach you how to solve a Sphere and a Cone!

Example 1: Solve the Sphere with the diameter of 10!

First thing we need to know is the formulas!

SA Sphere = 4πr $^2$

V Sphere = 4/3 πr $^3$

This is simple: To find the surface area we just need πr $^2$ times 4! The radius is half the diameter which is 5! So we enter 4 * π * $5^2$ :

The surface area is 315.159

Now let’s find the volume! Once again, it’s very simple! All we do is enter 4 / 3 * π * $5^3$ :

The Volume is 294.524. We have now solved the Sphere!

Example 2: Solve the Cone with the radius of 7 and a slant height of 11!

Once again, formulas!

SA Cone = πr $^2$ + πrs

V Cone = 1/3 πr $^2$ h

The Surface Area is simple: We just enter π * $7^2$ + π * 7 * 11:

The answer is 395.84

Volume is where it gets complicated! We need to find the height, but we don’t have it! To find the height, we need to use the formula:

√ $� l^2$ – $� r^2$

So we enter in our calculator: √ $� 11^2$ – $� 7^2$ The answer is 8.49!

To find the Volume, we enter in your calculator: 1/3 * π * 7 * $^2$ * 8.49

The answer is 138.67. We have now solved the Cone!

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