It is required to make a closed cylindrical tank of height 1 m and base diameter 140 cm from a metal sheet. How many square metres of the sheet are required for the same?

Radius of base of cylinder r = 140/ 2 = 70 cm 0.7 m and height h = 1 m
Total surface area of cylinder = 2πr(r + h)
= 2 × 22/7 × 0.7(0.7 + 1) = 4.4 × 1.7 = 7.48 m²
Hence, 7.48 square meter metal sheet is required to make the closed cylindrical tank.