Question

What is the surface area of a cylindrical ring if its outside diameter is 16 mm and its inside diameter is 10 mm? Round your answer to the nearest whole number.
A.92mm^2
B.118mm^2
C.385mm^2
D.123mm^2

Answer 1

S1=200.96
S2=78.5
Sring=200.96-78.5=122.46 ≈ D.123mm^2

Answer 2

Answer:

D. $123\ mm^2$

Step-by-step explanation:

The cylindrical ring has outside diameter of 16 mm and inside diameter of 10 mm.

The area of the outer circle,

$A_{outer}=\pi \cdot \dfrac{d^2}{4}=\pi \cdot \dfrac{16^2}{4}=64\pi\ mm^2$

The area of the inner circle,

$A_{inner}=\pi \cdot \dfrac{d^2}{4}=\pi \cdot \dfrac{10^2}{4}=25\pi\ mm^2$

So the area of the ring will be,

$A_{outer}-A_{inner}=64\pi-25\pi=39\pi=122.52\approx 123\ mm^2$