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Question
Fri February 17, 2012 By:

# 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.

Sat February 18, 2012
Here the A part is the area of steel used actually to make the cylindrical tank.
It is given 1/12th of the steel used was wasted. i.e. 1/12 A sq m of steel was wasted
So, steel used for construction reduces to A - 1/12 A = 11/12 A sq.m.
This value of steel is equal to the surface area of the tank = 87.12 sq.
Hence we arrive at the value of A, equating
11/12 A = 87.12
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