Let’s solve each surface area problem step by step.
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Problem 1: Rectangular Prism (dimensions: 5 ft, 4 ft, 3 ft)
Surface Area of a rectangular prism = 2(lw + lh + wh)
l = length = 5 ft
w = width = 4 ft
h = height = 3 ft
Calculate:
lw = 5 × 4 = 20
lh = 5 × 3 = 15
wh = 4 × 3 = 12
Sum = 20 + 15 + 12 = 47
Multiply by 2 → 47 × 2 =
94 sq ft
✔ Check: All faces accounted for — front/back, left/right, top/bottom. Correct.
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Problem 2: Cube (side = 6 in)
Surface Area of cube = 6 × side²
side = 6 in
side² = 6 × 6 = 36
6 × 36 =
216 sq in
✔ Check: A cube has 6 identical square faces. Each is 36 in² → total 216. Correct.
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Problem 3: Rectangular Prism (dimensions: 8 m, 4 m, 2 m)
Again: SA = 2(lw + lh + wh)
l = 8, w = 4, h = 2
lw = 8×4 = 32
lh = 8×2 = 16
wh = 4×2 = 8
Sum = 32 + 16 + 8 = 56
×2 → 56 × 2 =
112 sq m
✔ Check: Dimensions match diagram. Calculation correct.
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Problem 4: Cube (side = 10 cm)
SA = 6 × side²
side = 10 cm
side² = 100
6 × 100 =
600 sq cm
✔ Check: Simple cube formula applied correctly.
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Final Answer:
1) 94 sq ft
2) 216 sq in
3) 112 sq m
4) 600 sq cm
Parent Tip: Review the logic above to help your child master the concept of surface area worksheet 7th grade.
