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. 118mm2 B. 92mm2 C. 385mm2 D. 123mm2

Answer 1

Answer : The correct option is, (D) $123mm^2$

Step-by-step explanation :

As we are given,

The outside diameter = 16 mm

The inner diameter = 10 mm

First we have to determine the radius of outside and inner radius of the ring.

As we know that,

$Radius=\frac{Diameter}{2}$

$\text{Radius of outside of ring}=\frac{16mm}{2}=8mm$

$\text{Radius of inner of ring}=\frac{10mm}{2}=5mm$

Now we have to determine the surface of the ring.

$\text{Area of ring}=\text{Outer surface area of ring}-\text{Inner surface area ring}$

$\text{Area of ring}=\pi (\text{Radius of outside ring})^2-\pi (\text{Radius of inner ring})^2$

Now put all the given values in this expression, we get:

$\text{Area of ring}=3.14\times (8mm)^2-3.14\times (5mm)^2$

$\text{Area of ring}=200.96mm^2-78.5mm^2$

$\text{Area of ring}=122.46mm^2\approx 123mm^2$

Therefore, the surface area of cylindrical ring is $123mm^2$