What is the sum, in inches, of diameters J and K?

• A. 7 in.
• B. 11 in.
• C. 9 in.
• D. 5 in.

Answer: (C)

Diameters in the same circle are congruent, so each diameter covers the full width of the circle. If J and K are both diameters, they each have the circle’s diameter length, let's call it D. The sum of the two diameters is D + D = 2D. From the diagram, the circle’s diameter is 4.5 inches, so 2D = 2 × 4.5 = 9 inches.