Question

A CLOSED METALLIC CYLINDER HAS ITS BASE DIAMETER 56 CM 2.25 M HIGH.FIND THE COST OF THE METAL USED TO MAKE IT IF COSTS Rs.80 PER SQUARE METRE

Answer 1

Diameter of base of closed metallic cylinder = 56 cm
So, its radius; r = 562 = 28 cm = 0.28 m
Height; h = 2.25 m

Total surface area of metallic cylinder = 2πr(r+h) = 2×227×0.28(0.28+2.25) = 2×227×0.28×2.53 =4.4528 m2 
Cost of making per square meter of metal = Rs.80
So, total cost of making the whole metal = 4.4528×80 = Rs.356.224

Answer 2

Total area of the closed cylinder is = sum of two circles (top and bottom)+ curved surface area


$area \: = 2. \frac{\pi}{4} . {d}^{2} + \pi.d.h \\ area = 2. \frac{\pi}{4} .( {0.56}^{2} ) + \pi .(0.56).(2.25) \\ area = 0.4927 + 3.9584 \: = 4.4511sq.mt \\ total \: cost \: = 80 \times 4.4511 = 356.08 rupees$
Total cost = 356.08 ~ 357 rupees

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