Question

A cone of height $7$ cm and base radius $3$ cm is carved from a rectangular block of wood $10cm\times 5cm\times 2cm$. Find the % of wastage.

• A. $70\%$
• B. $46\%$
• C. $34\%$
• D. $43\%$

Answer 1

The correct option is C $34\%$

Volume of rectangular block $=$ $lbh=10\times 5\times 2=100{cm}^3$

Volume of cone $=$ $\frac{1}{3}\pi r^{2}h=\frac{1}{3}\times \frac{22}{7}\times 3\times 3\times 7=66{cm}^3$

% wastage $=$ $\frac{100-66}{100}\times 100=34$%