Question : Two circles with centres A and B of radii 6 cm and 4 cm, respectively, touch each other internally. If the perpendicular bisector of AB meets the bigger circle in P and Q, then the value of PQ is:
Option 1: $\sqrt{5}$ cm
Option 2: $2 \sqrt{35}$ cm
Option 3: $\sqrt{35} $ cm
Option 4: $2 \sqrt{5}$ cm
Correct Answer: $2 \sqrt{35}$ cm
Solution : AB = 6 – 4 = 2 cm The perpendicular bisector of AB meets the bigger circle in P and Q. The perpendicular chord bisector equals the radius of a circle. The perpendicular line bisects the chord. The perpendicular bisector bisects chord AB at C. AC = $\frac{AB}{2}$ = $\frac{2}{2}$ = 1 cm In a $\triangle ACB$, using Pythagoras's theorem, $(AP)^2=(AC)^2+(PC)^2$ ⇒ $(PC)^2=6^2–1^2$ ⇒ $(PC)^2=36–1$ ⇒ $(PC)^2=35$ ⇒ $PC=\sqrt{35}$ cm The length of PQ = 2 PC = $2\sqrt{35}$ cm. Hence, the correct answer is $2\sqrt{35}$ cm.
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Question : Two circles with their centres at O and P and radii 8 cm and 4 cm respectively touch each other externally. The length of their common tangent is:
Option 1: 8.5 cm
Option 2: $\frac{8}{\sqrt{2}}$ cm
Option 3: $8\sqrt{2}$ cm
Option 4: 8 cm
Question : Two circles of radii 5 cm and 3 cm intersect each other at A and B, and the distance between their centres is 6 cm. The length (in cm) of the common chord AB is:
Option 1: $\frac{4 \sqrt{13}}{3}$
Option 2: $\frac{2 \sqrt{14}}{3}$
Option 3: $\frac{2 \sqrt{13}}{3}$
Option 4: $\frac{4 \sqrt{14}}{3}$
Question : What is the length (in cm) of the transverse common tangent between two circles with radii 6 cm and 4 cm, given that the distance between their centres is 14 cm?
Option 1: $2 \sqrt{6}$
Option 2: $4 \sqrt{6}$
Option 3: $5 \sqrt{6}$
Option 4: $3 \sqrt{6}$
Question : Out of two concentric circles, the radius of the outer circle is 6 cm and the chord PQ of the length 10 cm is a tangent to the inner circle. Find the radius (in cm) of the inner circle.
Option 1: $4$
Option 2: $\sqrt{7}$
Option 3: $\sqrt{13}$
Option 4: $\sqrt{11}$
Question : Two circles of radii 8 cm and 3 cm, respectively, are 13 cm apart. AB is a direct common tangent touch to both the circles at A and B respectively then the length of AB is:
Option 1: 10 cm
Option 2: 12 cm
Option 3: 8 cm
Option 4: 6 cm
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