There are two circles that touch each other externally. Radius of the first circle with centre O is 12 cm. Radius of the second circle with centre A is 8 cm. Find the length of their common tangent BC.

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SSC CGL 2023 Tier-I Official Paper (Held On: 26 Jul 2023 Shift 1)
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  1. \( {6 \ \sqrt{6} }\) cm
  2. \( {8 \ \sqrt{3} }\) cm
  3. \( {8 \ \sqrt{2} }\) cm
  4. \( {8 \ \sqrt{6} }\) cm

Answer (Detailed Solution Below)

Option 4 : \( {8 \ \sqrt{6} }\) cm
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Detailed Solution

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Concept used:

If two circles touch each other externally, then the length of their common tangent = 2√r1r2 , where r1 and r2 are radius

Calculation:

F3 SSC Priya 7 9 24  D1

Radius of the first circle (r1) = 12 

Radius of the second circle (r2= 8

Then, according to the question,

the length of their common tangent BC

= 2√(12 × 8)

= 2√96

= 2 ×√(16 × 6)

= 8√6 cm

∴ The correct answer is 8√6 cm

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