Subject: General Aptitude · Chapter: Area · Exam: · Marks: · Difficulty:
A circular grassy plot of land, 42 m in diameter, has a path 3.5 m wide running round it outside. Find the cost of gravelling the path at ₹ 4 per square metre.
Answer
Answer (as printed):
Explanation
Radius of plot, $r=\left(\frac{42}{2}\right) \mathrm{m}=21 \mathrm{m}$. Radius of (plot + path), $R=(21+3.5) \mathrm{m}=24.5 \mathrm{m}$. Area of path $=\pi\left(R^{2}-r^{2}\right)=\pi\left[(24.5)^{2}-(21)^{2}\right]$ $$=\frac{22}{7} \times(24.5+21)(24.5-21)=\left(\frac{22}{7} \times 45.5 \times 3.5\right) \mathrm{m}^{2}=500.5 \mathrm{m}^{2} .$$ ∴ Cost of gravelling $=₹(500.5 \times 4)=₹ 2002$.