Question : Two circles of radii 8 cm and 3 cm, respectively, are 13 cm apart. AB is a direct common tangent touch to both the circles at A and B respectively then the length of AB is:
Option 1: 10 cm
Option 2: 12 cm
Option 3: 8 cm
Option 4: 6 cm
Correct Answer: 12 cm
Solution : The length of the direct common tangent AB, where $d$ is the distance between the centres of the two circles, and $r_1$ and $r_2$ are the radii of the two circles. $AB = \sqrt{d^2 - (r_1 - r_2)^2}$ Substituting the given values, $AB = \sqrt{(13)^2 - (8 - 3)^2} = \sqrt{169 - 25} = \sqrt{144} = 12 \text{ cm}$ Hence, the correct answer is 12 cm.
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Question : Two circles with their centres at O and P and radii 8 cm and 4 cm respectively touch each other externally. The length of their common tangent is:
Option 1: 8.5 cm
Option 2: $\frac{8}{\sqrt{2}}$ cm
Option 3: $8\sqrt{2}$ cm
Option 4: 8 cm
Question : Two circles with radii of 25 cm and 9 cm touch each other externally. The length of the direct common tangent is:
Option 1: 34 cm
Option 2: 30 cm
Option 3: 36 cm
Option 4: 32 cm
Question : In two circles centred at O and O’, the distance between the centres of both circles is 17 cm. The points of contact of a direct common tangent between the circles are P and Q. If the radii of both circles are 7 cm and 15 cm, respectively, then the length of PQ is equal to:
Option 1: 15 cm
Option 2: 17 cm
Option 3: 10 cm
Option 4: 22 cm
Question : What is the length (in cm) of the transverse common tangent between two circles with radii 6 cm and 4 cm, given that the distance between their centres is 14 cm?
Option 1: $2 \sqrt{6}$
Option 2: $4 \sqrt{6}$
Option 3: $5 \sqrt{6}$
Option 4: $3 \sqrt{6}$
Question : Two circles of radii 5 cm and 3 cm intersect each other at A and B, and the distance between their centres is 6 cm. The length (in cm) of the common chord AB is:
Option 1: $\frac{4 \sqrt{13}}{3}$
Option 2: $\frac{2 \sqrt{14}}{3}$
Option 3: $\frac{2 \sqrt{13}}{3}$
Option 4: $\frac{4 \sqrt{14}}{3}$
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