In the following figure, there are two circles that touch each other externally. The radius of the first circle with centre P is 25 cm. The radius of the second circle with centre Q is 4 cm. Find the length of their direct common tangent AB.

Figure is not to scale and is only for representational purpose

Radius of the first circle, $$r_1$$​ = 25cm

Radius of the second circle, $$r_2$$​= 4cm

The Circles touch each other externally.

Formula Used: The formula for the length of the direct common tangent between two circles is:

​$$L = \sqrt{d^2 - (r_1 - r_2)^2}​$$​​

where:

L is the length of the direct common tangent

d is the distance between the centers of the two circles

$$r_1$$​  and $$r_2$$​ are the radii of the two circles.

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