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The distance between the centres of two circles having radii 8 cm and 3 cm, is 13 cm. The length (in cm) of the direct common tangent of the two circles is
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- 15
- 16
- 18
- 12
- 15
Correct Option: D
As per the given in question , we draw a figure of two circles having radii 8 cm and 3 cm
As we know that , Length of direct common tangent = √(Distance between two centres)² - (r1 - r2)²
Length of direct common tangent = √13² - (8 - 3)²
Length of direct common tangent = √13² - 5²
Length of direct common tangent = √(13 + 5)(13 - 5)
Length of direct common tangent = √18 × 8 = 12 cm
