Question

how can i find the surface area of a oen rectangular box 7cm 4cm and 4cm high

Answer 1

I'm going to assume that the biggest face is the open side.

Length = 7 cm
Width = 4 cm
Height = 4 cm

You have two faces (front and back)
= 2 x length x height
= 2 x 7 x 4 = 2 x 28 cm² = 56 cm²

You have two sides (left and right)
= 2 x width x height
= 2 x 4 x 4 = 2 x 16 cm² = 32 cm²

You have one base (bottom)
= 1 x length x width
= 1 x 7 x 4 = 28 cm²

Adding it up:
= 56 cm² + 32 cm² + 28 cm²

Answer:
116 cm²

Answer 2

hope it helps :)