Question

PLS MATHS EXPERT PLS ANSWER ASAP I AM GIVING OUT ALL MY POINTS!!!!!

Q4: There are two cylinders. The first is of radius 7 and height 4 and the second is of radius 6 and height 7. Which cylinder has the larger surface area?
A. the second cylinder
B. the first cylinder

Q5: Find the surface area of a cylinder whose base is a circle of radius 21 cm and whose height is 9 cm.Use
=22/7

Q6: Hannah and Michael were calculating the surface area of a cylinder of height 28 and radius 9. Hannah found the surface area to be
180
,and Michael found it to be 666
.Who is correct?
A. Hannah
B. Michael

Answer 1

4. A

5. 3960 cm²

6. B

Explanation:

#4. The surface area of a cylinder is denoted by: A = 2πr² + 2πrh, where r is the radius and h is the height. Plug the given values for the two cylinders in:

1st cylinder: A = 2πr² + 2πrh = 2π * 7² + 2π * 7 * 4 = 154π

2nd cylinder: A = 2πr² + 2πrh = 2π * 6² + 2π * 6 * 7 = 156π

So, the second cylinder has the larger surface area: A.

#5. Use the area equation again here: A = 2πr² + 2πrh.

The radius is 21 and the height is 9, so:

A = 2πr² + 2πrh

A = 2 * (22/7) * 21² + 2 * (22/7) * 21 * 9 = 3960 cm²

#6. Use the area equation again here: A = 2πr² + 2πrh.

The radius is 9 and the height is 28, so:

A = 2πr² + 2πrh

A = 2π * 9² + 2π * 9 * 28 = 666π

Thus, Michael is correct: B.

Answer 2

Q4: A. the second cylinder

Q5:
`$\text{Surface Area} =3960 cm^2$`

Q6: B. Michael

Explanation:

Q4:

Cylinders:

- The first is of radius 7 and height 4

- The second is of radius 6 and height 7

`\text{Surface Area} =2\pi r^2+2\pi r h`

Cylinder 1:

`C_(1)SA =2\pi r^2+2\pi r h`

`C_(1)SA =2\pi (7)^2+2\pi (7) (4)`

`C_(1)SA =98\pi +56\pi\\C_(1)SA =154\pi \text{square units}`

Cylinder 2:

`C_(2)SA =2\pi r^2+2\pi r h`

`C_(2)SA =2\pi (6)^2+2\pi (6) (7)`

`C_(2)SA =72\pi +84\pi\\C_(2)SA =156\pi \text{square units}`

Q5:

Cylinder:

Radius = 21 cm

Height = 9 cm

`$\pi =(22)/(7) $`

`\text{Surface Area} =2\pi r^2+2\pi r h`

`$\text{Surface Area} =2(22)/(7) (21)^2+2(22)/(7) (21) (9)$`

`$\text{Surface Area} =882(22)/(7) +378(22)/(7) $`

`$\text{Surface Area} =2772 +1188$`

`$\text{Surface Area} =3960 cm^2$`

Q6:

Cylinder of height 28 and radius 9.

`\text{Surface Area} =2\pi r^2+2\pi r h`

`\text{Surface Area} =2\pi (9)^2+2\pi (9) (28)`

`\text{Surface Area} =162\pi +504\pi`

`\text{Surface Area} =666\pi`

Michael is correct.