Exams › SSC CGL (Prelims) › General

Two circles have radii 9 cm and 4 cm. The distance between their centers is 13 cm. What is the length of the direct common tangent?

1. 12 cm
2. 10 cm
3. 8 cm
4. 15 cm

Correct answer: 12 cm

Solution

For a direct common tangent, the tangent length is \(\sqrt{d^2-(r_1-r_2)^2}\). Here \(d=13\), \(r_1-r_2=5\), so the length is \(\sqrt{13^2-5^2}=\sqrt{144}=12\) cm.

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