Can someone help me with this?!

1 Answer
May 19, 2018
  1. B
  2. C
  3. B

Explanation:

Question 19
Note that since #AB# is a tangent
#/_OAB= 90^circ# and we can apply the Pythagorean Theorem.

Using #r# as the radius (#r=abs(OA)=abs(OC)#)

We have
#color(white)("XXX")abs(OA)^2+abs(AB)^2=abs(OB)^2#

#color(white)("XXX")r^2+15^2=(r+9)^2#

#color(white)("XXX")cancel(r^2)+225=cancel(r^2)+18r+81#

#color(white)("XXX")18r=144#

#color(white)("XXX")r=8#
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Question 20
This is a straight application of the Pythagorean Theorem.
(Note that the extended base length is irrelevant to the right triangle).
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Question 21
Of all rectangular shapes the square encloses the greatest area for any given perimeter.
(The option of a circle can be ruled out without calculation since its perimeter/circumference will involve a factor of #pi# and therefore can not exactly match the given length of 60 feet).