2.)

**Explain why you need to find the circumference of a circle to find the surface area of a cylinder?**

*This is what I think.*

You need to find the circumference of a circle to find the surface area of a cylinder because in order to find the surface area, in the end you have to add it up to get your TOTAL SURFACE AREA.

4.)

**Estimate the surface area of each cylinder. Then, calculate each surface area to the nearest cenimetre.**

*This is what I did.*

On the first cylinder it is d = 7cm and the height is 30cm.

*remember to write down your formula because you can lose a half mark on a test!*

(pi x r 2) + (pi x d x h) = Total surface area

A.) d/2 = r

7/2 = 3.5cm2

(3.14 x 3.5 x 3.5)+(3.14 x 7 x 30) = 697.86cm2

38.46cm2 + 659.4cm2 = 697.86cm2

Total Surface Area = 697.86cm2

(pi x r 2)+(pi x d x h) = Total surface area

B.)(3.14 x 10 x 10)+(3.14 x 20 x 22) = 1695.6cm2

314cm2 + 1381.6cm2 = 1695.6cm2

Total Surface Area = 1695.6cm2

6.)

**Use the formula, (pi x r 2)+(pi x d x h) to calculate the surface area of each object. Give your answer to the nearest hundredth of a square unit**.

A.)(3.14 x 1.25 x 1.25)+(3.14 x 2.5 x 10)

4.90cm2 + 78.5cm2

Total Surface Area = 83.4cm2

B.) d/2= r

5/2=2.5

(3.14 x 2.5 x 2.5)+(3.14 x 5 x 7)

19.62cm2 + 109.9cm2

Total Surface Area = 129.52cm2

8.)

**Anu wants to re-cover the cylindrical stool in his bedroom. how much material will he need if there is no overlap and he does not cover the bottom of the stool.**

*This is what I did.*

Formula = (pi x r x r)+(pi x d x h)

d/2= r

42/2 = 21

(3.14 x 21 x 21)+(3.14 x 42 x 32)

1384.71cm2 + 4220.16cm2 - 21 =

Total Surface Area = 5583.87cm2

Here is a link on cylinder and a little bit about Volume!

Here is a link to a helpful video.

Cylinder Problems from 7.3

A.) Volume = (pi x r x r) x h

d/2 = r 8/2 = r r = 4 cm

*(3.14 x 4 x 4) = 50.24 cm^2*

50.24 cm^2 x 12 cm = 602.88 cm^3

Volume = 602.88 cm^3

B.) Volume = ( pi x r x r) x h

d/2 = r 2/2 = r r = 1 cm

(3.14 x 1 x 1) = 3.14 cm^2

3.14 cm^2 x 7 = 21.98 cm^3

Volume = 21.98 cm^3

C.) Volume = ( pi x r x r ) x h

d/2 = r 12/2 = r r = 6 cm

( 3.14 x 6 x 6 ) = 113.04 cm^2

113.04 cm^2 x 37.5 = 4239 cm^3

Volume = 4239 cm^3

D.) Volume = ( pi x r x r ) x h

d/2 = r 4.5/2 = r r = 2.25 cm

( 3.14 x 2.25 x 2.25 ) = 15.89625 cm^2

15.89625 cm^2 x 19.5 = 309.976875 cm^3

Volume = 309.976875 cm^3

Cylinder problems from 7.4

A.) Yes, he does have enough small prisms.

B.) The volume of the new prism is 22.4672^3

Here is what I did.

V= B x h / 2 x h

V = 5.6 x 6.8 / 2 = 19.04 x 1.18 = 22.4672^3

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