SSC CHSL 6 Mar 2018 Shift 3 Paper

Section: English Language

Question : 6 of 100

Marks: +1, -0

If the radius of a circle is decreased to 25% of its original value, calculate the percentage decrease in the area of the circle.

Solution:

Let the radius of the circle initially =

r

= 20cm
⇒ Area =

A = πr ^2 = π(20) ^2 = 400π

New radius =

r'=20-(25/100×20)=15

cm
⇒ New Area =

A′ = π(15)^2 = 225π

∴ Percent decrease in area =

(400π−225π)/400π ×100

175/4 =43.75%

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