Circle A and circle B are congruent. CD is a chord of both circles. If AB = 8 ft and CD = 6 ft, how long is a radius?

6 ft
5 ft
7 ft
8 ft

Question

Circle A and circle B are congruent. CD is a chord of both circles. If AB = 8 ft and CD = 6 ft, how long is a radius?

6 ft
	5 ft
	7 ft 
	8 ft

anonymous · Answer

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anonymous · Answer

i choose 7 i am not sure if i am right

mathmate · Answer

Let AB and CD meet at a point E.
The lines AB and CD are perpendicular, which means that the triangle CEB is a right triangle, with hypotenuse CB, which in turn equals the radius.
Since AB=8', EB=4'.
CD=6', so CE=3'.
Can you now find the radius?

anonymous · Answer

so my answer is wrong then

mathmate · Answer

7 is not correct.  You need to calculate the answer based on sound mathematical reasoning.  Guessing will not give you the right answer most of the time.  Can you follow my explanation and come up with a calculated answer?

anonymous · Answer

then my other answer would be 5  and ok

mathmate · Answer

Yes, 5 is correct.  I hope you understand how you got it so that in the exam, you will still get the right answer.