Question

if the radius of circle is diminished by 10% then its area is diminished be (a)10% (b)19% (c)20% (d)36% i want reasoning also

Answer 1

Let, the radius be r. Then area of circle = PI * r * r
Radius is diminished by 10% so New radius, R = r - ( 10 * r / 100 )
= > R = 0.9 * r
New area = PI * R * R
Putting value R = 0.9 * r
New area = 0.81 * PI * r *r
Diffrence = Old area - New area
=> Diffrence = PI * r * r - 0.81 * PI * r * r
=> Diffrence = 0.19 * PI * r * r
Diminished area = 19%

Answer 2

Answer:19

Step-by-step explanation:by simple equation (2a-a*a/100)

Put a=10

Then

(2*10-100/100)

(20-1)=19

In increasing case the equation become

(2a+a*a/100)