Subject: General Aptitude · Chapter: Area · Exam: · Marks: · Difficulty:
A square lawn with side 100 m long has a circular flower bed in the centre. If the area of the lawn, excluding the flower bed, is $8614 \mathrm{m}^{2}$, the radius of the circular flower bed is
(a)21 m
(b)31 m
(c)41 m
(d)None of these
Answer
Answer (as printed): A
Explanation
Area of the flower bed $=[(100 \times 100)-8614] \mathrm{m}^{2}$ $$=1386 \mathrm{m}^{2} .$$ Let the radius of the circular flower bed be $R$ metres. $$\text { Then, } \pi R^{2}=1386 \Rightarrow R^{2}=\frac{1386 \times 7}{22}=441 \Rightarrow R=21 \mathrm{m} \text {. }$$