A container in the shape of a frustum of a cone having diameters of its two circular faces as 35 cm and vertical height 14 cm, is completely filled with oil. if each cm3 of oil has mass 1.2 g them find the cost of oil in the container if it costs Rs.40 per Kg.
Given, Diameter of top of container =35 cm Radius of top =R=235​=17.5 cmDiameter of bottom of container =30 cm Radius of bottom =r=230​=15 cm1cm3 of oil, so, cost of 1 kg oil = Rs. 40Height of frustum =h=14 cm Volume of frustum of cone =31​πh (R2+r2+Rr)cm3 Volume of oil in container =31​×722​×14(17.52+152+17.5×15)=322​×2×7993.75=334925​ Volume of oil in container =11641.667cm3  or 11641.667×1.2×1.2 g   ..........  each cm3 of oil has mass 1.2 g=13970.000 g or 13.970 kg ............ (AS 1000 g =1 kg) Cost of 13.970 kg oil = Rs 40×13.970 = Rs. 558.8