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  1. Each edge of a regular tetrahedron is 3 cm, then its volume is
    1. 9√2
      c.c.
      4
    2. 27√3 c.c.
    3. 4√2
      c.c.
      9

    4. 9√3 c.c.
Correct Option: A

Area of the tetrahedron =
1
area of base × height
3

Area of the base =
3
× (side)²
4

=
3
× 3 × 3 =
9√3
cm²
44

Now, length of the perpendicular in the equilateral triangle
= √3² -
3
²
2

= √9 -
9
=
3√3
cm
42

∴ Height = √
3√3
² -
3
²
22

= √
27
-
3
= √6 cm.
44

∴ Required area =
1
×
9√3
× √6 =
9√3
cu.cm.
344



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