Let’s solve each problem step by step.
We’ll start with the
Rectangular Prisms (also called cuboids).
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Formula Reminder:
For a rectangular prism with length = l, width = w, height = h:
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Volume = l × w × h
-
Surface Area = 2×(l×w + l×h + w×h)
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#### 1. Rectangular Prism: 2cm × 3cm × 5cm
- Volume = 2 × 3 × 5 =
30 cm³
- Surface Area = 2×(2×3 + 2×5 + 3×5) = 2×(6 + 10 + 15) = 2×31 =
62 cm²
✔ Check: 6+10+15=31 → ×2 = 62 ✔️
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#### 2. Rectangular Prism: 2cm × 9cm × 3cm
- Volume = 2 × 9 × 3 =
54 cm³
- Surface Area = 2×(2×9 + 2×3 + 9×3) = 2×(18 + 6 + 27) = 2×51 =
102 cm²
✔ Check: 18+6+27=51 → ×2 = 102 ✔️
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#### 3. Rectangular Prism: 4m × 4m × 12m
Note: Two sides are 4m — so it’s like a long box with square ends.
- Volume = 4 × 4 × 12 =
192 m³
- Surface Area = 2×(4×4 + 4×12 + 4×12) = 2×(16 + 48 + 48) = 2×112 =
224 m²
✔ Check: 16+48+48=112 → ×2 = 224 ✔️
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#### 4. Rectangular Prism: 70mm × 110mm × 20mm
- Volume = 70 × 110 × 20
First: 70 × 20 = 1400
Then: 1400 × 110 = 1400 × 100 + 1400 × 10 = 140,000 + 14,000 =
154,000 mm³
- Surface Area = 2×(70×110 + 70×20 + 110×20)
Calculate each part:
70×110 = 7,700
70×20 = 1,400
110×20 = 2,200
Sum = 7,700 + 1,400 + 2,200 = 11,300
×2 =
22,600 mm²
✔ Check: 7700+1400=9100; 9100+2200=11300 → ×2=22600 ✔️
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Now for the
Cubes.
Formula for cube with side = s:
-
Volume = s³ = s × s × s
-
Surface Area = 6 × s² (since 6 faces, each is s×s)
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#### 5. Cube: 6cm
- Volume = 6 × 6 × 6 =
216 cm³
- Surface Area = 6 × (6×6) = 6 × 36 =
216 cm²
✔ Interesting — same number! But different units. ✔️
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#### 6. Cube: 30mm
- Volume = 30 × 30 × 30 = 900 × 30 =
27,000 mm³
- Surface Area = 6 × (30×30) = 6 × 900 =
5,400 mm²
✔ Check: 30²=900 → ×6=5400 ✔️
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#### 7. Cube: 8m
- Volume = 8 × 8 × 8 = 64 × 8 =
512 m³
- Surface Area = 6 × (8×8) = 6 × 64 =
384 m²
✔ Check: 8²=64 → ×6=384 ✔️
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#### 8. Cube: 5cm
- Volume = 5 × 5 × 5 =
125 cm³
- Surface Area = 6 × (5×5) = 6 × 25 =
150 cm²
✔ Check: 5²=25 → ×6=150 ✔️
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All calculations double-checked and correct.
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Final Answer:
Rectangular Prisms:
1. Volume: 30 cm³, Surface Area: 62 cm²
2. Volume: 54 cm³, Surface Area: 102 cm²
3. Volume: 192 m³, Surface Area: 224 m²
4. Volume: 154,000 mm³, Surface Area: 22,600 mm²
Cubes:
5. Volume: 216 cm³, Surface Area: 216 cm²
6. Volume: 27,000 mm³, Surface Area: 5,400 mm²
7. Volume: 512 m³, Surface Area: 384 m²
8. Volume: 125 cm³, Surface Area: 150 cm²
Parent Tip: Review the logic above to help your child master the concept of surface area worksheet 7th grade.