Practice the questions of McGraw Hill Math Grade 8 Answer Key PDF Lesson 22.1 Surface Area of Solid Figures to secure good marks & knowledge in the exams.
McGraw-Hill Math Grade 8 Answer Key Lesson 22.1 Surface Area of Solid Figures
Exercises
CALCULATE SURFACE AREA
Question 1.
Answer:
Surface area of the cube = 96 square cm.
Explanation:
Side of the cube = 4 cm.
Surface area of the cube = 6 × Side of the cube × Side of the cube
= 6 × 4 × 4
= 24 × 4
= 96 square cm.
Question 2.
Answer:
Surface area of the cuboid = 160 square cm.
Explanation:
Length of the cuboid = 10 inches.
Width of the cuboid = 2 inches.
Height of the cuboid = 5 inches.
Surface area of the cuboid = 2(Length of the cuboid × Width of the cuboid) + 2(Width of the cuboid × Height of the cuboid) + 2(Height of the cuboid × Length of the cuboid)
= 2(10 × 2) + 2(2 × 5) + (5 × 10)
= 2(20) + 2(10) + 2(50)
= 40 + 20 + 100
= 60 + 100
= 160 square cm.
Question 3.
Answer:
Surface area of the cuboid = 72 square m.
Explanation:
Length of the cuboid = 6 m.
Width of the cuboid = 2 m.
Height of the cuboid = 3 m.
Surface area of the cuboid = 2(Length of the cuboid × Width of the cuboid) + 2(Width of the cuboid × Height of the cuboid) + 2(Height of the cuboid × Length of the cuboid)
= 2(6 × 2) + 2(2 × 3) + 2(3 × 6)
= 2(12) + 2(6) + 2(18)
= 24 + 12 + 36
= 36 + 36
= 72 square m.
Question 4.
Answer:
Surface area of the cylinder = 402.285 square inches.
Explanation:
Height of the cylinder = 12 inches.
Radius of the cylinder = 4 inches.
Surface area of the cylinder = 2π r h + 2π r²
= 2π × 4 × 12 + 2π × 4 × 4
= 2π × 48 + 2π ×16
= 2Ï€ (48 + 16)
= 2π × 64 ( π = \(\frac{22}{7}\))
= 128 × \(\frac{22}{7}\)
= \(\frac{2816 }{7}\)
= 402.285 square inches.
Question 5.
Answer:
Surface area of the cuboid = 340 square cm.
Explanation:
Length of the cuboid = 10 cm.
Width of the cuboid = 6 cm.
Height of the cuboid = 10 cm.
Surface area of the cuboid = 2(Length of the cuboid × Width of the cuboid) + 2(Width of the cuboid × Height of the cuboid) + 2(Height of the cuboid × Length of the cuboid)
= 2(10 × 6) + 2(6 × 10) + 2(10 × 10)
= 2(60) + 2(60) + 2(100)
= 120 + 120 + 100
= 240 + 100
= 340 square cm.
Question 6.
Answer:
Surface area of the cylinder = 358.285 square inches.
Explanation:
Height of the cylinder = 16 inches.
Radius of the cylinder = 3 inches.
Surface area of the cylinder = 2π r h + 2π r²
= 2π × 3 × 16 + 2π × 3 × 3
= 2π × 48 + 2π ×9
= 2Ï€ (48 + 9)
= 2π × 57
= 114 × \(\frac{22}{7}\)  (As π = \(\frac{22}{7}\))
= \(\frac{2508 }{7}\)
= 358.285 square inches.