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?
Answer & explanation
Correct answer: option 3
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.