A and B are the centres of two circles with radii 11 cm

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A and B are the centres of two circles with radii 11 cm and 6 cm respectively. A common tangent touches these circles at P and Q respectively. If AB = 13 cm., then the length of PQ is

1. 13 cm.
2. 17 cm.
3. 8.5 cm.
4. 12 cm.

Correct Option: D

As per the given in question , we draw a figure of two circles with radii 11 cm and 6 cm respectively

Here , AB = 13 cm.
PQ = √(AB)² - (r₁ - r₂)²
PQ = √(13)² - (11 - 6)²
PQ = √169 -25 = √144 = 12 cm.