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What is the radius of the circle in cm?

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enter image description here

In the above figure, the rectangle at the corner measures 6 cm x 12 cm. What is the radius of the circle in cm?

posted Jul 16, 2014 by Manish Tiwari

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1 Answer

+3 votes

enter image description here

Using Pythagoras' Theorem (see Hint in above diagram)
for the right-angled triangle in the figure alongside,
(r - a)^2 + (r - b)^2 = r^2
Now, a = 6 cm and b = 12 cm. So,
(r - 6)^2 + (r - 2)^2 = r^2 or
r^2 - 2(6)r + 36 + r^2 - 2(12)r + 144 = r^2. This simplifies to
r^2 - 36r + 180 = 0. On factorizing, we get
(r - 30)(r - 6) = 0.
Thus, the radius of the circle is 30 cm.

answer Jan 27, 2015 by Jaspalsingh Parmar
well done.Perfect
You are great
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