Question

QUESTION ==>

The Sum of Diameters of two Circles is 2.8 m and the difference of their Circumferences is 0.88 m. Find the Radii of the two Circles in cm.

Answer 1

$\underline\bold{\huge{ANSWER \: :}}$

Let the diameter of first circle be D1

Let the diameter of second circle be D2

Similarly let the radius of first circle be r1 and that of the second circle be r2.

Given, D1+ D2 = 2.8

=> 2r1 + 2r2 = 2.8

=> 2 (r1 + r2) = 2.8

=> r1 + r2 = (2.8/2) m = 1.4 m ......... (I)

Also, 2πr1 - 2πr2 = 0.88

=> 2 π (r1 - r2) = 0.88

=> r1 - r2 = (0.88)/{2×(22/7)}

=> r1 - r2 = (0.88)/(44/7)

=> r1 - r2 = 0.14 m .......... (II)

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Now, adding two equations, we get :

r1 + r2 + r1 - r2 = 1.4 + 0.14

=> 2r1 = 1.54

=> r1 = 0.77 m or 77 cm
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If r1 = 0.77 m, then :

r1 + r2 = 1.4

=> 0.77 + r2 = 1.4

=> r2 = 1.4 - 0.77

=> r2 = 0.63 m or 63 cm.
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Hence, the required answer is the radii of two circles (in cm) are 77 cm and 63 cm.

Answer 2

❤ HERE IS YOUR ANSWER DEAR ❤
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Say, the diameter of first circle be D1 and similarly the diameter of second circle be D2
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Accordingly, let the radius of first circle be r1 and that of the second circle be r2.
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Given, D1+ D2 = 2.8 

=> 2r1 + 2r2 = 2.8

=> 2 (r1 + r2) = 2.8

=> r1 + r2 = (2.8/2) m = 1.4 m ......... (I) 

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Also we can write,

2πr1 - 2πr2 = 0.88

=> 2 π (r1 - r2) = 0.88

=> r1 - r2 = (0.88)/{2×(22/7)} 

=> r1 - r2 = (0.88)/(44/7)

=> r1 - r2 = 0.14 m .......... (II) 

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Now, adding two equations, we get :

r1 + r2 + r1 - r2 = 1.4 + 0.14

=> 2r1 = 1.54

=> r1 = 0.77 m or 77 cm
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If r1 = 0.77 m, then :

r1 + r2 = 1.4

=> 0.77 + r2 = 1.4

=> r2 = 1.4 - 0.77

=> r2 = 0.63 m or 63 cm. 
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HENCE, YOUR PROBLEM IS SOLVED

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