Q.- A closed cylinderical petrol storage tank is of diameter 4.2m and 4.5m in height. how much steel was actually used if 1/12th of the steel actually used was wasted in making the tank? sir, my query is that the solution given on "topper learning site" is: TSA of tank= 2*22/7*2.1*6.6=87.12sq.meter. let A sq m be actually used: A(1-1/12)=87.12 A=12/11*87.12 A=95.04. i didnt understand the solution regarding the 'A' part?? please explain.