# Cuboid

• Aug 24th 2008, 09:54 PM
devi
Cuboid
If each side of a cuboid is doubled,its volume is
(a)doubled
(b)becomes 4 times
(c)becomes 6 times
(d)becomes 8 times
• Aug 24th 2008, 10:02 PM
Jhevon
Quote:

Originally Posted by devi
If each side of a cuboid is doubled,its volume is
(a)doubled
(b)becomes 4 times
(c)becomes 6 times
(d)becomes 6 times

Let $x$ be the side length of a cuboid.

the volume is given by:

$V = x^3$

now change $x$ to $2x$. what happens to $V$? how many times larger does it become?
• Aug 24th 2008, 10:07 PM
ticbol
Quote:

Originally Posted by devi
If each side of a cuboid is doubled,its volume is
(a)doubled
(b)becomes 4 times
(c)becomes 6 times
(d)becomes 6 times

d) becomes 6 times as posted is a typo. It should have been becomes 8 times.

Original volume = a*b*c = abc
When each side is doubled, new volume = (2a)(2b)(2c) = 8abc.
• Aug 24th 2008, 10:29 PM
devi
Quote:

Originally Posted by ticbol
d) becomes 6 times as posted is a typo. It should have been becomes 8 times.

Original volume = a*b*c = abc
When each side is doubled, new volume = (2a)(2b)(2c) = 8abc.

Yes it is a typo.But the answer was doubled.
• Aug 24th 2008, 10:50 PM
ticbol
Quote:

Originally Posted by devi
Yes it is a typo.But the answer was doubled.

You mean the answer is a)?
Cannot be.

A dictionanary says a cuboid is a rectangular parallelepiped. So it looks like any box of six rectangular faces. (A square is also a rectangular, by the way).
So the volume is length*width*height.
If all those 3 dimensions are doubled, then the original volume is doubled only according to your book?