Question

A right cylinder has a circumference of 14π cm. Its height is 3 times the radius. Identify the lateral area and the surface area of the cylinder rounded to the nearest tenth.

For lateral area I keep getting 294. As for surface area, I keep getting 308. These answers are wrong, but I've tried solving it so many times and I still continue to get the same result. >.< Someone please explain this to me.

Answer 1

you forgot pi is what you did wrong

circumference=2pi(r)
14pi=2pi(r)
dividde both sides by pi
14=2r
divide by 2
7=r
height is 3 times radius so 7 times 3=21
lateral area=area around the cylinder or the net area form minust the 2 cirlcues on top so basically find height times circumference so
circumference=14 pi
height=21
14pi times 21= 294pi
pi aprox=3.14 so multiply
294 times 3.14=923.16 cm^2

Answer 2

L=2πR
L=14π
2πR=14π
R=14π/2π=7 - the radius
h=3R=3*7=21 -the height

S(l)=2πRh=Lh=14π*21=294π≈923,6 - the lateral area
S(s)=2πR²+Lh=2π*7²+294π=2π*49+294π=98π+294π=
=392π≈1231,5 -the surface area