Question

A circular piece of cardboard with a diameter of 25 cm will be made into a conical hat 10 cm high by cutting a sector off and joining the edge to form a cone. Determine the angle subtended by the sector which was removed.

Answer 1

@ganeshie8

Answer 2

@~Gelmhar what's your choices?

Answer 3

the answer must be 216degrees.

Answer 4

@~Gelmhar if I'm going to help I need to know what are your choices and what do you think it may be

Answer 5

What are your choices or are there any?

Answer 6

nope, i need the solution for this on how they arrive on that 216 degrees.... there is no choices...

Answer 7

144 degrees

Answer 8

That's the answer

Answer 9

Don't know where you got 216

Answer 10

Let me explain

Answer 11

based on the book, the answer must be 216

Answer 12

If the circular piece of cardboard has a diameter of 25cm, then its radius, which is also the cone's slant height is 12.5 cm.

If the conical hat is 10 cm high, then its height is 10 cm.

If its height is 10 inches and its slant height is 12.5 inches, then find the cone's radius:

a² + b² = c²

radius² + cone's height² = slant height²

a² + 10² = 12.5²

a² + 100 = 156.25

a² = 56.25

a = 7.5 inches is the radius of the cone's base.

If the radius is 7.5 inches, then its circumference, which is also the arc of the sector that was used, is C = 2πr.

C = 2π(7.5) = 15π <=arc of sector used.

Since the circular piece of cardboard has a diameter of 25cm, then its circumference is 25π, so the sector removed would have an arc length of 25π - 15π = 10π.

10π/(25π) = 2/5 of circle

2/5 x 360⁰ = 144⁰

Answer 13

I already worked it out on notepad

Answer 14

I have more people to help do you mind if I have a medal

Answer 15

Tweet me @flashp on openstudy if you need help

Answer 16

the source that you get at yahoo is incorrect ..

Answer 17

Yahoo? What in the world is Yahoo.

Answer 18

now this sector of the circle is made into a cone so the
area of cone=area of sector agree??

Answer 19

@~Gelmhar

Answer 20

yup

Answer 21

@gorv

Answer 22

@ganeshie8 can you continue his work :D

Answer 23

@perl