question_answer 1)

Find the cost of polishing a circular table-top of diameter 1.6 m, if the rate of polishing is ` \[\text{15/}{{\text{m}}^{\text{2}}}.(\text{Take}\pi =\text{3}.\text{14})\]

Answer:

                Diameter of the table-top \[~=\text{1}.\text{6 m}\] \[\Rightarrow \]               Radius of the table-top (r) \[\text{= }\frac{\text{1}\text{.6}}{\text{2}}\text{m = 0}\text{.8m}\]      \[\therefore \] Area of the table-top \[=\pi {{r}^{2}}\] \[\text{= 3}\text{.14  }\!\!\times\!\!\text{  (0}\text{.8}{{\text{)}}^{\text{2}}}\text{ }{{\text{m}}^{\text{2}}}\] \[\text{= 3}\text{.14  }\!\!\times\!\!\text{  0}\text{.64 }{{\text{m}}^{\text{2}}}\] \[\text{= 2}\text{.0096 }{{\text{m}}^{\text{2}}}\] \[\therefore \] Cost of polishing the table-top   = `\[2.0096\times 15=\] ` 30.144