I'll help you solve these surface area problems for prisms and cylinders. Let me work through each one step by step.
First, let me identify what I need to calculate:
- Surface area of rectangular prisms (cubes/boxes)
- Surface area of triangular prisms
- Surface area of cylinders
The formulas I'll use:
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Rectangular prism: SA = 2(lw + lh + wh) where l=length, w=width, h=height
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Triangular prism: SA = 2(area of triangle base) + (perimeter of triangle × height of prism)
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Cylinder: SA = 2πr² + 2πrh (or 2πr(r + h))
Let me solve each problem:
Problem A: Rectangular prism with dimensions 10 cm × 5 cm × 8 cm
SA = 2(10×5 + 10×8 + 5×8)
SA = 2(50 + 80 + 40)
SA = 2(170)
SA = 340 cm²
Problem B: Triangular prism with base triangle (base=6 cm, height=4 cm) and prism length=9 cm
Area of triangle = (1/2) × 6 × 4 = 12 cm²
Perimeter of triangle = 6 + 5 + 5 = 16 cm (assuming it's isosceles with sides 5, 5, 6)
SA = 2(12) + 16×9
SA = 24 + 144
SA = 168 cm²
Problem C: Rectangular prism with dimensions 12 cm × 4 cm × 7 cm
SA = 2(12×4 + 12×7 + 4×7)
SA = 2(48 + 84 + 28)
SA = 2(160)
SA = 320 cm²
Problem D: Triangular prism with base triangle (base=8 cm, height=3 cm) and prism length=10 cm
Area of triangle = (1/2) × 8 × 3 = 12 cm²
Perimeter of triangle = 8 + 5 + 5 = 18 cm (assuming isosceles)
SA = 2(12) + 18×10
SA = 24 + 180
SA = 204 cm²
Problem E: Cube with side 9 cm
SA = 6 × s² = 6 × 9² = 6 × 81 = 486 cm²
Problem F: Cylinder with radius 5 cm and height 12 cm
SA = 2πr² + 2πrh = 2πr(r + h)
SA = 2π(5)(5 + 12) = 2π(5)(17) = 170π
Using π ≈ 3.14: SA = 170 × 3.14 = 533.8 cm²
Problem G: Rectangular prism with dimensions 15 cm × 6 cm × 4 cm
SA = 2(15×6 + 15×4 + 6×4)
SA = 2(90 + 60 + 24)
SA = 2(174)
SA = 348 cm²
Problem H: Cylinder with radius 4 cm and height 10 cm
SA = 2πr(r + h)
SA = 2π(4)(4 + 10) = 2π(4)(14) = 112π
Using π ≈ 3.14: SA = 112 × 3.14 = 351.68 cm²
Problem I: Triangular prism with base triangle (base=7 cm, height=5 cm) and prism length=11 cm
Area of triangle = (1/2) × 7 × 5 = 17.5 cm²
Perimeter of triangle = 7 + 6 + 6 = 19 cm (assuming isosceles)
SA = 2(17.5) + 19×11
SA = 35 + 209
SA = 244 cm²
Final Answer:
A: 340 cm²
B: 168 cm²
C: 320 cm²
D: 204 cm²
E: 486 cm²
F: 533.8 cm² (or 170π cm²)
G: 348 cm²
H: 351.68 cm² (or 112π cm²)
I: 244 cm²
Parent Tip: Review the logic above to help your child master the concept of volume and surface area worksheets.