The diameters of two circles with centre A and B are 16cm and 30cm respectively. If the area of a circle with centre C is equal to the difference of areas of other two circles, then find the circumference of the circle with centre C.
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First find areas of circles A & B
radius A = 16/2 = 8cm
radius B = 30/2 = 15cm
area A = 22/7 x 8 x 8
= 201.14 cm square
area B = 22/7 x 15 x 15
= 707.14 cm square
diff in area = 707.14 - 201.14
= 506
find radius of C = 22/7 x r^2 = 506
r^2 = 161
r = sq.root of 161
circumference = 2 x 3.14 x √161
= 6.28√161
radius A = 16/2 = 8cm
radius B = 30/2 = 15cm
area A = 22/7 x 8 x 8
= 201.14 cm square
area B = 22/7 x 15 x 15
= 707.14 cm square
diff in area = 707.14 - 201.14
= 506
find radius of C = 22/7 x r^2 = 506
r^2 = 161
r = sq.root of 161
circumference = 2 x 3.14 x √161
= 6.28√161
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