In Fig. 16.57, from a cuboidal solid metallic block, of dimensions 15 cm × 10 cm × 5 cm, a cylindrical hole of diameter 7 cm is drilled out. Find the surface area of the remaining block.(Take π=22/7)
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Total surface area = 583 sq.cm
Step-by-step explanation:
Dimensions of cuboid = 15 cm × 10 cm × 5 cm
Surface Area of cuboid = 2lw + 2lh + 2hw = 2 (150 + 50 + 75) = 550 sq.cm
Height of cylinder = 5cm
Radius of cylinder = 7/2 - 3.5cm
Curved surface area of cylinder = 2πrh
2 * round surface of ends of cylinder = 2πr²
2πrh - 2πr² = 2πr (h-r) = 2 * 22/7 * 3.5 (5 - 3.5)
= 2 * 22/7 * 3.5 * 1.5
= 33
Total surface area = surface area of cuboid + CSA of cylinder - 2 area of ends of cylinder
= 550 + 33
= 583 sq.cm
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