A line from point A is drawn that is tangent to the circle at point B. A secant is also drawn from point A to the circle intersecting it at points C and D. If AB = 42 cm and AC = 21 cm, then what is the ratio between AB and CD?

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SSC CHSL Exam 2024 Tier-I Official Paper (Held On: 10 Jul, 2024 Shift 2)
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Answer (Detailed Solution Below)

Option 1 : 2 ∶ 3
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Detailed Solution

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Given:

A line from point A is tangent to the circle at point B.

A secant is drawn from point A to the circle intersecting it at points C and D.

AB = 42 cm (tangent segment)

AC = 21 cm (secant segment from A to C)

Formula Used:

The Power of a Point theorem states:

The square of the length of the tangent segment (AB) from a point to a circle is equal to the product of the lengths of the segments of the secant (AC and AD) from the same point.

AB2 = AC × AD

Calculation:

F1 Savita Banking 9-10-24 D12 

Let AD be the length of the secant segment from A to D.

According to the Power of a Point theorem:

AB2 = AC × AD

422 = 21 × AD

1764 = 21 × AD

AD = 1764 / 21

AD = 84 cm

CD = AD - AC

CD = 84 cm - 21 cm

CD = 63 cm

The ratio between AB and CD is:

AB : CD = 42 : 63

Simplify the ratio:

42 / 21 : 63 / 21

2 : 3

The ratio between AB and CD is 2 : 3.

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