Radii of two circles are 20 cm and 4 cm. Length of direct common tangent is 30 cm. What is the distance between their centres?

36 cm 38 cm 34 cm 32 cm

34 cm

Let the distance between their centers be x cm. According to the formula, = 30 = \(\sqrt {(x^2 - (20 - 4)^2) }\) = 30 = \(\sqrt {(x^2 - (16)^2) }\) = 900 = x^2 - 256 = x^2 = 900 + 256 = 1156 = x = 34 Therefore, distance between them is 34 cm.