In the given figure, AB = 30 cm and CD = 24 cm. What is the value (in cm) of MN?

Answer: Option A

Let bigger circle radius = R
Let Smaller circle radius = r
Am = 15
Cm = 12
According to the question
R² - 15² = r² - 12²
[By Pythagoras theorem]
R² - r² = 15² - 12²
R² - r² = 81
$$\sqrt{{\text{R}}^2-{\text{r}}^2}$$   = 9
MN = 2NP = 9 × 2 = 18 cm