In the figure 7.12, a cylindrical wrapper of flat tablets is shown. The radius of a tablet is 7 mm and its thickness is 5 mm. How many such tablets are wrapped in the wrapper ?

Thickness of a tablet, h = 5 mm

Radius of cylindrical wrapper, R =

\(\frac{14}{2}\) = 7 mm

Height of wrapper (H) = 10 cm

= 10 × 10 mm

= 100 mm

Let n be the number of tablets wrapped in the wrapper.

\(n = \frac{\text{ Volume of the cylindrical wrapper} }{\text{ Volume of each tablet } }\)

\( \Rightarrow n = \frac{\pi R^2 H}{\pi r^2 h}\)

\( \Rightarrow n = \frac{\left( 7 \right)^2 \times 100}{\left( 7 \right)^2 \times 5} = 20\)

Thus, 20 tablets are wrapped in the wrapper.