a dartboard consists of 2 concentric circles. the probability of hitting the inner circle is 16%. if the outer circle has a diameter of 20 inches. what is the radius of the inner circle?

Question

a dartboard consists of 2 concentric circles.  the probability of hitting the inner circle is 16%.  if the outer circle has a diameter of 20 inches.  what is the radius of the inner circle?

jim_thompson5910 · Answer

we're given this 

|dw:1361327427251:dw|

jim_thompson5910 · Answer

the first step is to find the area of the outer circle

jim_thompson5910 · Answer

use 

A = pi*r^2

anonymous · Answer

a=31.4

jim_thompson5910 · Answer

no it's not r times 2

it's r squared

jim_thompson5910 · Answer

A = pi*r^2

A = 3.14*10^2

A = 314.159265

anonymous · Answer

right  10*10

jim_thompson5910 · Answer

that's the area of the larger circle

jim_thompson5910 · Answer

sry, if you're just using 3.14 for pi, then it's 314

jim_thompson5910 · Answer

now if the probability of hitting the inner circle is 16%, then the are of the smaller circle is 16% of the area of the larger circle

jim_thompson5910 · Answer

Area of Smaller Circle = 16% of Area of Larger Circle 

Area of Smaller Circle = 16% of 314

Area of Smaller Circle = 0.16 * 314

Area of Smaller Circle = ???

anonymous · Answer

16% of 314=50.24

jim_thompson5910 · Answer

good

jim_thompson5910 · Answer

now use this to solve for r

A = pi*r^2

50.24 = 3.14*r^2

keep going to find r

anonymous · Answer

got it  working on it

anonymous · Answer

4

jim_thompson5910 · Answer

very good

jim_thompson5910 · Answer

that's your final answer

anonymous · Answer

so simple  thanks for explaining

jim_thompson5910 · Answer

yw