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CBSE Class 10 Standard Math 2025 All Sets Solved Paper

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Question : 5 of 20
Marks: +1, -0
In the adjoining figure, the sum of radii of two concentric circles is 16 cm. The length of chord AB which touches the inner circle at P is 16 cm. The difference of the radii of the given circles is
Solution:  
Let r1r_1 be the radius of the inner circle and r2r_2 be the radius of the outer circle.
From the problem, we know that r1+r2=16 cmr_1 + r_2 = 16\,\text{cm}
The length of chord AB is 16 cm, so half of it (AP) is 8 cm.
Using the Pythagorean theorem in triangle OAP,
we have r22=r12+82r_2^2 = r_1^2 + 8^2
which simplifies to r22=r12+64r_2^2 = r_1^2 + 64
Now, substitute r2=16−r1r_2 = 16 - r_1 into the equation r22=r12+64r_2^2 = r_1^2 + 64
and solve for r1r_1 and r2r_2.
The difference of the radii is 8 cm.
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