Q13 of 32 Page 13

A closed cuboid water tank is made of steel sheet that is 2.5 cm thick. The outer dimensions of the tank are 2.15 m × 1.5 m × 1.1 m. Find the inteernal dimensions and total surface area of the tank.

External dimensions of the cube are
l = 215 cm, b = 150 cm, h = 110 cm
Since the sheet is 2.5 cm thick, the internal dimensions are
l = (215 - 5) cm = 210 cm, b =(150 - 5) cm = 145 cm,
h = (110 - 5) cm = 105 cm
∴ Total surface area of the tank = 2(lb + bh + lh)
                              = 2 × (2.15 × 1.5 + 1.5 × 1.1 + 2.15 × 1.1) m3
                              = 2 × (3.225 + 1.65 + 2.365) m3                              
                              = 14.48 m3

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