Question

A Bangle of inner radius 2.1 cm and thickness 0.7 cm and height 0.5 cm. Find the volume of material used for bangle.(approx)

• A. $2.5{\text{cm}}^3$
• B. $15.8{\text{cm}}^3$
• C. $10.40{\text{cm}}^3$
• D. $5.4{\text{cm}}^3$

Answer 1

The correct option is D $5.4{\text{cm}}^3$

Given,
Solid: Hollow Cylinder
Inner radius of bangle $r_i=2.1\text{cm}$
Thickness of bangle $=0.7\text{cm}$
Outer radius of bangle$r_o=2.1+0.7=2.8\text{cm}$
Height of bangle, $h=0.5\text{cm}$

Volume of bangle
= Volume of hollow cylinder
$=\pi r_o^{2}h-\pi r_i^{2}h=h\pi (r_0^2-r_i^2)=0.5\pi ({2.8}^2-{2.1}^2)=0.5\times \frac{22}{7}(7.84-4.41)=\frac{11}{7}\times 3.43=5.39\cong 5.4{\text{cm}}^3$

Volume of bangle is $5.4{\text{cm}}^3$.