60, because 120 is bigger than a right angle, and the picture shows that it is definitely smaller than a right angle.
The answer is D, 8$. One easy way to do it is to take 10% of 40, which is 4, and double it.
The radius is 10, so the diameter is 20. This means the parts of the diameter (the chord through the center P) to the left and right of the vertical chord have lengths 16 and 4, respectively.
Because the horizontal chord is a diameter, the vertical chord is cut in half, so its parts above and below the diameter both have length <em>x</em>.
Now, by the intersecting chord theorem,
16×4 = <em>x</em> × <em>x</em>
or
<em>x</em> ² = 64
so that
<em>x</em> = 8
The first one is 156, the second 420 the third is 6,138 and the forth one is 64.
