Question : Two circles of radii 15 and 18 cm touch each other externally. What is the length (in cm) of the direct common tangent to the two circles?
Option 1: $18 \sqrt{6}$
Option 2: $12 \sqrt{15}$
Option 3: $30 \sqrt{6}$
Option 4: $6 \sqrt{30}$
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Correct Answer: $6 \sqrt{30}$
Solution :
Given: $R_1$ = 15 cm
$R_2$ = 18 cm
Thus, direct common tangent = $2\sqrt{R_1R_2}$
= $2\sqrt{15×18}$
= $6 \sqrt{30}$ cm
Hence, the correct answer is $6 \sqrt{30}$.
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