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A trapezium has one pair of parallel sides; its area is half the sum of the parallel sides × the distance between them. A rhombus has area half the product of its diagonals. The total surface area of a cuboid is the area of its 6 faces, 2(lb + bh + hl), and a cube has 6 equal squares, 6a². The four walls of a room have area 2h(l + b).
✓ You passed this lesson’s test.
Flat parts add up — “a surface area is the total of the flat faces you can see”
Use it for: Painting rooms, wrapping boxes, fields shaped like a trapezium, and the mensuration chapter of Class 8 maths.
🧮 Check your own sums with the free Ratio calculator — it shows the working.
Check: 2 × 50 ÷ (12 + 8) = 100 ÷ 20 = 5, the height ✓
▶ Watch it animatedWork it out in your head or on paper, type the answer and press Check. Stuck? Press “Show me how”.
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20 sums. Check each answer, then go to the next one. Get 16 or more right to pass.
🏅 Sign in with Google to earn the 🎁 Surface Area Star badge when you pass — and a certificate when you finish all 8 lessons of Part 8 · Class 8. You can still take the test without signing in.
Why does it work? When should you use it? Ask in English, मराठी or हिंदी.
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