if radius of a circle is dimnished by 10% then its area is dimnished by
a) 10%
b) 19%
c) 20%
d) 36%

• let old r=r
  new r=0.9r (100-10)/100= 0.9
  old area=3.14 * r^2
  new area=3.14 * 0.81r^2
  % decrease= (3.14 r^2-3.14 * 0.81 r^2)*100/3.14 r^2
  =19%
• 11 years agoHelpfull: Yes(14) No(0)
• let the radius be 100 then after increasing it is 90
  area after change = pie*90^2
  normal area = pie*100^2
  area diminished percentage = (10000-8100)/10000=19%
• 11 years agoHelpfull: Yes(10) No(0)
• apply ab formula: a+b+(ab/100)=-10-10+(10*10/100)=-19% decrease
• 11 years agoHelpfull: Yes(6) No(0)
• let the reduced area is pie(90 r/100)^2
  and original area is pie(r)^2
  so difference is (19/100).
  answer is 19%
• 11 years agoHelpfull: Yes(2) No(0)
• B
  When radius reduces by 10% then remaining 90%radius would makeup to 81%of original area. (90%r X 90%r)
• 11 years agoHelpfull: Yes(1) No(0)
• formula for any 2D fig ... decrease in area=(2x-x^2/100)% and increase in area=(2x+x^2/100)%
  (2*10-10^2/100)%=19%
• 11 years agoHelpfull: Yes(1) No(0)
• ans is b.
  
• 11 years agoHelpfull: Yes(1) No(2)
• Initially let us assume radius of circle as 10.Then the area is 100.By diminishing radius by 10% then the area is 81.Hence there is decrease in 19% of actual area
  
• 11 years agoHelpfull: Yes(0) No(0)
• initial radius=R
  new radius=R-0.1R=0.9R
  %DECREASE IN AREA=1-0.9*0.9/1=19%
• 11 years agoHelpfull: Yes(0) No(0)
• 19% answer..
• 11 years agoHelpfull: Yes(0) No(0)
• here area means = r*r.
  radius decreased by 10%.(100-10 = 90)
  r = 90.
  r * r = 90*90 = 810/10 = 81.
  so 100 - 81 = 19%
• 9 years agoHelpfull: Yes(0) No(0)
• (90/100)*(90/100)*100=81
  100-81=19%
• 9 years agoHelpfull: Yes(0) No(0)
• Let the original radius 'r' = 10cm
  
  keeping the π constant, Area 'A' is proportional to 'r'
  
  Therefore A = 100 sq.cm
  
  Diminished by 10%, 'r' = 9cm
  
  therefore, New Area = 81 sq.cm
  
  % Area diminished = (100 - 81) / 100 = 19%
• 7 years agoHelpfull: Yes(0) No(0)
• 100% of r to 10% reduction i.e., 0.9r
  now, area of circle is pi*r*r
  i.e., pi*(0.9r)*(0.9r)=0.81*pi*r*r=81%
  area reduced from 100% to 81% is 19% loss.
• 4 years agoHelpfull: Yes(0) No(0)