Question

Answer based on the following
Two circles of radii $8$ units and $4$ units are drawn. The distances between there centres is $20$ units.
What is the length of direct common tangent?

• A. $16$
• B. $12$
• C. $8\sqrt{6}$
• D. $32$

Answer 1

The correct option is C $8\sqrt{6}$

Length of direct common tangent $=\sqrt{{20}^2-(8-4{)}^2}$
$=\sqrt{400-16}$
$=4\sqrt{24}=8\sqrt{6}$