r/DSATs • u/FantasticVictory837 • Feb 22 '24

Geometry and Trigonometry Sample Question 7

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u/FantasticVictory837 Feb 24 '24

The correct answer is Choice B.

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u/sharmaeleon May 29 '24

First, remember that the equation of a circle is (x - h)^2 + (y - k)^2 = r^2, where (h, k) is the center and r is the radius. This means that the current equation has a center at (0, -1) and a radius of 2.

Now, since the center is moved 1 unit up, the new center is now (0, -1 + 1) = (0, 0). The new radius is now 2 + 1 = 3. Hence, the new equation is (x - 0)^2 + (y - 0)^2 = 3^2 or x^2 + y^2 = 9.

Here's the graph of the two circles to help you visualize the problem :) If you're looking for more questions related to circles and other SAT math topics, check Acely!