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# Maths surface area watch

1. The radius of a sphere is 3cm
The radius of a base od a cone is 3cm
The surface area of the sphere equals the total surface area of the cone
Work out the slant height of the cone

I got 3 but it is wrong!
I did: 36pi=12pi+slant height
Slant height= 36pi/12pi=3
2. (Original post by Lucofthewoods)
The radius of a sphere is 3cm
The radius of a base od a cone is 3cm
The surface area of the sphere equals the total surface area of the cone
Work out the slant height of the cone

I got 3 but it is wrong!
I did: 36pi=12pi+slant height
Slant height= 36pi/12pi=3
what did you get when finding the perpendicular height of the cone?
3. (Original post by TSRian123454321)
what did you get when finding the perpendicular height of the cone?
you dont need that
4. Surface area of sphere = 4 × πr²

Total surface area of the cone = πrl + πr² (where l=slant height)

Subbing in r=3 for the sphere and cone

36π=3πl + 9π
You cannot plus the π together
5. (Original post by Lucofthewoods)
you dont need that
oh, SA, not V

oops
6. (Original post by Pentaquark)
Surface area of sphere = 4 × πr²

Total surface area of the cone = πrl + πr² (where l=slant height)

Subbing in r=3 for the sphere and cone

36π=3πl + 9π
You cannot plus the π together
what do i from there?
7. (Original post by Lucofthewoods)
what do i from there?
Move the 9pi to the other side You need to get the slant height so move everything to one side.
From there you should know how to get l (slant height)

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