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formula for area of a circle formula for area of a circle in our daily to daily life we use many objects that are circular in shape such as wheels flower beds etc because of this problem of finding areas related to circular shapes have a big practical importance and it can be practiced by solving area related problems if `r is the radius of the circle then formula for area of a circle will be:formula for area of circle will be r2 formula for area of semi-circle will be r2 2 formula for area of circle will be r2 4 in above example pie is the greek letter that indicates the ratio of the circumference and diameter of a circle 22 7 or 3.14 not exact we can also solve those problems in which we have two concentric circles whose areas are enclosed if `r and `r are radius of two concentric circles then the equation will be r2 r2 r2 r2 r r r ­ r let s take a close look on some different type of example of the area of the circle know more about derivative rules math.tutorvista.com page no 1/4

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p. 2

example 1 find the area of circle when we have radius that is equals to 6.4 cm solution we know that the area a of a circle is r2 a area r2 22 7 6.4 6.4 cm2 128 73 cm2 example 2 find the area of circle with radius as 10 cm solution given radius r 10 cm area of circle r2 here r 10 cm so we have 22 7 10 10 cm2 314.28 sq cm if we do not have the radius directly then we can calculate the radius from the diameter when diameter is given and after that we use same formula that is r2 for calculating the area of circle example 3 the area of circle with the diameter is 15 cm solution area of the circle .d2 4 3.142 15 15 4 176.73 sq cm example 4 find the area of circle whose circumference is 22 cm we can also find the area of circle when we have circumference so below is the solution solution let `r be the radius of the circle then circumference 22 cm 2r 22 2 22 7 r 22 r 22 7 area of circle r2 22 7 7 2 7 2 cm2 38.5 cm learn more trapezoidal rule math.tutorvista.com page no 2/4

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p. 3

above were the examples of area of circles and besides this we can also find the area for the particular sectors that may be minor and major and to do this we follow their respected formulas this is all about formula for area of a circle using this formula we can find the area of circle example 2 the area of a circle with diameter as 8cm is solution area of the circle .d2/4 3.142 8 8/4 50.265 sq cm math.tutorvista.com page no 4/4

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