As per IS: 303 and 10701, the thickness of 5 ply plywood boards for structural purpose are available in
- A6 mm and 9 mmCorrect
- B12 mm and 16 mm
- C16 mm and 19 mm
- D10 mm and 15 mm
Solution
Concept
Plywood is made of an odd number of veneers (plies). Each ply count has standard thicknesses given in the IS codes.
Step-by-step solution
1. Plywood is made with 3, 5, 7, 9 or more plies. 2. Thin boards (3-6 mm) are mostly 3 ply. 3. 5 ply boards are commonly 6 mm and 9 mm thick. 4. Thicker boards like 12, 15, 16 and 19 mm need 7 ply or more. 5. So the answer is A: 6 mm and 9 mm.
Explanation
As the number of plies increases, the board thickness increases. For 5 ply plywood, the standard thicknesses commonly listed are 6 mm and 9 mm. Higher thicknesses belong to 7 ply and 9 ply boards.
Why the other options are wrong
B: 12 mm and 16 mm are mainly 7 ply or more. C: 16 mm and 19 mm are thick boards with 7 to 9 or more plies. D: 10 mm is not a standard plywood thickness.
Shortcut
Each ply is about 1.2 to 2 mm thick, so 5 plies give roughly 6 to 9 mm.
Common mistake
Choosing the thicker values by thinking 5 ply means a heavy board.
Correct answer: A) 6 mm and 9 mm