Subject: General Aptitude · Chapter: Area · Exam: · Marks: · Difficulty:
What will be the cost of gardening a strip of land inside around a circular field, at the rate of ` 85 per sq. metre ? I. The area of the field is 1386 sq. metres. II. Breadth and length of the field are in the ratio of 3 : 5 respectively.
Answer
SELF-PRACTICE — the source book printed no answer.
Nothing is invented here, so this question has no answer on record.
Explanation
I. $\pi R_{1}{ }^{2}=1386 \Leftrightarrow R_{1}{ }^{2}=\left(1386 \times \frac{7}{22}\right) \Leftrightarrow R_{1}=21 \mathrm{m}$. II. $\mathrm{R}_{2}=(21-1.4) \mathrm{m}=19.6 \mathrm{m}$. $\therefore \quad$ Area $=\pi\left(R_{1}{ }^{2}-R_{2}{ }^{2}\right)=\frac{22}{7} \times\left[(21)^{2}-(19.6)^{2}\right] \mathrm{m}^{2}$. Thus, the required cost may be obtained. ∴ I and II together will give the answer. ∴ Correct answer is (e).