Two circles which are not congruent touch externally the sum of their areas is 130π sqcmannd the distance between their centres is 14 cm.find radii of circles
Answers
See the above attachment
Given :-
- Sum of areas of both circular plots = 130π .
- Distance between their centres = 14 m.
To Find :-
- Radii of the circles ?
Solution :-
Let us assume that, radius of bigger plot is R m and radius of smaller plot is r m.
so,
→ R + r = Distance between their centre = 14m. -------- Eqn.(1)
and,
→ πR² + πr² = 130π
→ π(R² + r²) = 130π
→ R² + r² = 130 ------------ Eqn.(2)
now, from Eqn.(1) ,
→ (R + r) = 14
squaring both sides,
→ R² + r² + 2Rr = 196
putting value of Eqn.(2),
→ 130 + 2Rr = 196
→ 2Rr = 196 - 130
→ 2Rr = 66
→ Rr = 33 ----------------- Eqn.(3)
now, we know that,
- (a - b)² = (a + b)² - 4ab.
so, using Eqn.(1) and Eqn.(3) now,
→ (R - r)² = (R+r)² - 4*R*r
→ (R - r)² = (14)² - 4*33
→ (R - r)² = 196 - 132
→ (R - r)² = 64
→ (R - r) = 8 .
adding the result in Eqn.(1) , we get,
→ (R + r) + (R - r) = 14 + 8
→ 2R = 22
→ R = 11 m.
therefore,
→ R + r = 14
→ 11 + r = 14
→ r = 14 - 11
→ r = 3 m.
therefore, the radii of the circles is 11m and 3m.
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