I have made a rectangular parallelopiped by joining two cubes side by side made by Mita, whose edge is 8 cm in length. Let us calculate the total surface area and the length of the diagonal of the rectangular parallelopiped which is made in this way. [Let me do it myself] Hints: The length of the rectangular parallelopiped which is made = (8+8) cm = 16 cm, breadth = 8 cm, height = 8 cm.

If two cubes are placed side by side. The new length of the parallelopiped

= (8+8) = 16 cm

breadth = 8 cm

height = 8 cm.

\therefore Total area of the rectangular parallelopiped

= 2(16 × 8 + 16 × 8+8 × 8) sqcm.

= 2(128+128+64) sqcm = 2 × 320=640 sqcm

∴ Total area of the rectangular parallelopiped

= 2(16 × 8+16 × 8+8 × 8) sqcm.

= 2(128+128+64) sqcm = 2 × 320 = 640 sqcm.

\therefore Diagonal of the rectangular parallelopiped

=\sqrt{(16)^2+(8)^2+(8)^2}=\sqrt{256+64+64}=\sqrt{384}

= 8 \sqrt{6} cm

If the height of a rectangular parallelopiped is increased, its volume will be increased.