Answer:
30 cm
[tex]863.5\ \text{cm}^2[/tex]
Step-by-step explanation:
d = Diameter of cylinder = 4 cm
n = Number of times the strip of paper is turned = [tex]2\dfrac{1}{2}=2.5[/tex]
Diameter of the cylinder will be approximately equal to the diameter of the paper wound. Length of one turn will be circumference of the paper
Circumference of the paper
[tex]c=\pi d\\\Rightarrow c=3\times 4\\\Rightarrow c=12\ \text{cm}[/tex]
Total length of the paper will be the number of turns multiplied by the length of one turn
[tex]l=nc\\\Rightarrow l=2.5\times 12\\\Rightarrow l=30\ \text{cm}[/tex]
Length of the strip of paper is 30 cm.
2.
l = Slant height = 10 cm
d = Base diameter = 10 cm
r = Radius of base = [tex]r=\dfrac{d}{2}=\dfrac{10}{2}=5\ \text{cm}[/tex]
Total surface area of cone is given by
[tex]S=\pi r^2+\pi rl\\\Rightarrow S=\pi r(r+rl)\\\Rightarrow S=3.14\times 5(5+5\times10)\\\Rightarrow S=863.5\ \text{cm}^2[/tex]
The total surface area of cone is [tex]863.5\ \text{cm}^2[/tex].
