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the area of the region between two concrete circle is 3168 CM square find the radius of the two circle first their sum is 42 cm and their difference is 28 CM |
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Answer» Question is not clear, if the sum and difference of RADII are given, the radii can be solved. without USING info regarding area of region.R1 + R2 = 42R1 - R2 = 28-----------------2R1 = 70R1 = 35R2 = 7However, I feel this question is combination of two questions to find radii where1. area of region and sum of radii are give2. area of region and difference of radii are givenlet us try solving 1let SMALLER RADIUS be rbigger radius = 42 - rarea of region = 3168π{42-r)^2 - r^2) = 3168(1764 + r^2 - 84r - r^2) = 3168*7/22. (π = 22/1)1764 - 84r = 100884r = 1764 - 100884r = 756r = 756/84r= 9bigger radius = 42 - r = 42 - 9 = 33hence radii are 9 and 33Q2.let smaller radius be rbigger radius = r + 28area of region = 3168π((r+28)^2 - r^2) = 3168(r^2 + 56r + 784 - r^2) = 3168*7/2256r + 784 = 100856r = 1008 - 78456r = 224x = 224/56x= 4bigger radius = 28+4 = 32hence radii are 4 and 32 |
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