Associated Topics || Dr. Math Home || Search Dr. Math

### Unit Conversions

```
Date: 11/15/97 at 19:54:31
From: Jenna
Subject: Unit conversions

How many cups are in 4 liters?
```

```
Date: 11/15/97 at 20:47:02
From: Doctor Guy
Subject: Re: Unit conversions

The answer to this question depends on how precise you want to be.
The difficulty is that liters and cups are in two different
measurement systems, and it is not very easy to convert between them.

If you want this answer only very roughly, you can say that a liter
is a little bit more than a quart, so 4 liters is a bit more than
4 quarts. Then each quart is 2 pints, and each pint is 2 cups, so
4 liters is a bit more than 16 cups, say about 17 cups.

However, if you want more accuracy than this, we will have to look up
the equivalents somewhere, say on a soda bottle. I have a bottle of
raspberry seltzer water that says that it has 20 fluid ounces, and
that is equivalent to 591 milliliters. There are 8 fluid ounces in a
cup, so this bottle has 2-and-a-half cups, or 2.5 cups.

591 milliliters is 0.591 liters, because there are 1000 milliliters
(or ml, or cc, which means cubic centimeters) in one liter.

I can then set up a proportion, using the information I found from
this bottle:

0.591 liters / 2.5 cups = 4 liters / c cups

which I can also write this way:

0.591      4
_____  =  ____
2.5       c

To solve this, algebra books tell you that when two fractions are
equal, then the cross-products must also be equal. Therefore, 0.591
times c equals 4 times 2.5, or 0.591c = 10.0 .

Then I use a calculator to divide both sides by 0.591, and I get
that c is approximately 16.92 cups, which was about what I said in the
first place.

-Doctor Guy,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
```
Associated Topics:
Middle School Terms/Units of Measurement

Search the Dr. Math Library:

 Find items containing (put spaces between keywords):   Click only once for faster results: [ Choose "whole words" when searching for a word like age.] all keywords, in any order at least one, that exact phrase parts of words whole words

Submit your own question to Dr. Math
Math Forum Home || Math Library || Quick Reference || Math Forum Search