# Find the length of PQ :

A and B are centres of two circles of radii 11 cm and 6 cm, respectively. PQ is a direct common tangent to the circles, If AB=13 cm, then length of PQ will be

- 17 cm
- 12 cm
- 13 cm
- 8.5 cm

**Answer: (2) 12 cm **

**Explanation:-
**According to the question,

In the figure –

Common tangent CE = (13

^{2}– 5

^{2})

^{1/2}

= (169 – 24)

^{1/2}

= (144)

^{1/2}

= 12 cm

Then, the length of common tangent is 12 cm.

Hence, the answer is (2) 12 cm.