http:// www meritnation com /ask-answer/question/ in-the- area-of-a-circle-if- its-radius-is-increased-by-4/ areas-related-to-circles/ 3777090 1 New radius = r + 40/100 x r - Maths - Areas Related to Circles

Question

http:// www meritnation com /ask-answer/question/ in-the-
area-of-a-circle-if- its-radius-is-increased-by-4/
areas-related-to-circles/ 3777090
1 New radius = r + 40/100 x r
= r(140-100)
why is 100 added to the numerator??
2 Increase in surface area = [pi (1 4r sq ) - pir sq ]/ pir sq
why is original area not only subtracted but also divided by new
area

Manbar Singh · Accepted Answer

Here is the complete solution

Let the original radius of the circle = rOriginal area of circle, A = πr2Now, rate of increase = 40%Increase in radius = 40% of r = 40100r = 2r5Now, new radius, r1 = original radius + increase in radius⇒r1 = r + 2r5 = 7r5New area,A1 = πr12 = π7r52 = 4925πr2Now, increase in area = A1 - A = 4925πr2 - πr2 = 2425 πr2      Increase % = increase in areaoriginal area×100%⇒increase % = 2425πr2πr2×100%⇒increase %  = 2425×100% = 96%