Question

the difference of areas of two concentric circles is 770cm square and the difference their radii is 7cm find the radius of each circle.​

Answer 1

Answer:

π (R² - r²) is 770 ( according to question)

Step-by-step explanation:

π (R + r ) ( R - r ) is 770

22/7 *7 (R + r ) is 770

R + r. is 770/22 is 36

so R is 14 and r is 7

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Answer 2

Answer:

$21 \: cm$

Step-by-step explanation:

Solution,

Let the radii be R and r

R - r = 7

Therefore,

πR² - πr² = 770

π (R^{2}- r^{2}) = 770

π(R + r)(R - r) = 770

π(7 + r + r)(7 + r - r) = 770

22(7 + 2r) = 770

22 × 7 + 44r = 770

154 + 44r = 770154+44r=770

770 - 154 = 14r770−154=14r

616 = 14r

r = 14 cm

Radii of other circle = R

R = 14 + 7

R = 21 cm.