If the arean of circle is 56 what is radius??

2 Answers
Joe North
Jun 4, 2018

The radius of the circle is #sqrt(A/pi)~~4.2#.

Explanation:

The area of a circle is given by #pir^2#, where #r# is the radius of the circle. We know what the area is, and #pi# is a constant, so we can solve for the radius:

#A=pir^2rarr56=pir^2rarrr^2=56/pirarrr=+-sqrt(56/pi)~~4.2#.

(We know we have to use the positive square root because a negative radius wouldn't make sense!)

Bill Jorgensen
Jun 4, 2018

#r=2sqrt(14pi)/(pi)~~4.22#

Explanation:

#A_"circle" = pir^2#

#56 = pir^2#

#56/pi = r^2#

#+-sqrt(56/pi) = sqrt(r^2)#

We can ignore the negative solution because a radius cannot be negative.

#r=2sqrt(14pi)/(pi)#

#r=2sqrt(14pi)/(pi)~~4.22#

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