Three circles touch each other externally. The distance between their centre is 5 cm, 6 cm and 7 cm. Find the radii of the circles:
A
2 cm, 3 cm, 4 cm
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B
3 cm, 4 cm, 1 cm
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C
1 cm, 2.5 cm, 3.5 cm
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D
1 cm, 2 cm, 4 cm
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Solution
The correct option is A 2 cm, 3 cm, 4 cm AB = 5 cm = x + y BC = 6 cm = y + z AC = 7 cm = z + x
∴ 2(x + y + z) = 5 + 6 + 7 = 18 cm ∴ x + y + z = 9 cm ∴ x = (x + y + z) - (y + z) = 9 - 6 = 3 cm ∴ x + y = 5 cm ∴ y = 5 - x = 5 - 3 = 2 cm ∴ z = 6 - y = 6 - 2 = 4 cm ∴ x = 3 cm y = 2 cm and z = 4 cm