(solved)Question 23 SSC-CGL 2020 March 3 Shift 1

Question 23
SSC-CGL 2020 Mar 3 Shift 1

A circular park is in the form of a ring of inner and outer circumference 440 m and 506 m. The cost of levelling at Rs. 6 per square meter is?

Solution in Detail

Area to be levelled is the difference of areas of the outer and inner circles. We can write

Area = $\displaystyle \frac{506^2}{4\pi} - \frac{440^2}{4\pi}$

$\displaystyle = \frac{1}{4\pi}(506 + 440)(506 - 440)$

Use π = 22/7

Area $\displaystyle = \frac{7}{4 \times 22} \times (946) \times (66)$

$\displaystyle = 4966.5$

$\displaystyle \therefore$ cost $\displaystyle = 6 \times 4966.5 $

= 29799 Rs. Ans!