Question 176597
A){{{1.05^2}}}=1.1025  so error is 1.1025-1=.1025(100)=10.25% 
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B)if the incorrect diameter is 796 mm then the correct diameter is 796/1.05=
758.095mm. incorrect radius=796/2=398 mm or .398 m....correct radius =758.095/2=379.05mm or .379 m 
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incorrect={{{(pi)(.398)^2=.497 (m)^2}}}
correct=={{{(pi)(.379)^2=.451 (m)^2}}}
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checking error percentage with actual numbers.497-.451=.046:error % is .046/.451=.10197(100)=10.2% error 
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C) I will leave binomial theorem to you