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Convert the fraction 9 / 45 to a percent. %

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Convert the fraction 9 / 45 to a percent. %

'; truevalue1[1]='20'; question1[2]='

Convert the fraction 0.024 / 0.48 to a percent. %

'; truevalue1[2]='5'; question1[3]='

If the sugar glucose is 40 % carbon, what is the number of grams of carbon in 370 grams of glucose? g

'; truevalue1[3]='148'; question1[4]='

If ocean water is 3 % salt, how many grams of salt are in 50 grams of ocean water? g

'; truevalue1[4]='1.5'; question1[5]='

A cup of coffee weighs 300 grams. If it contains 9 grams of sugar, what is the percentage of the sugar in the coffee? %

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If 5 grams of sugar are dissolved in 195 grams of water, what is the percent of sugar in the resulting solution? (Be careful with this question. Take a look at the equation for Percent given in the above discussion). %

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Percents

A. Percents and Fractions:
A percent is a way of expressing something as a part of 100. Percents can be related to fractions and decimals as follows:

Likewise, 10 % is actually 10 parts per 100, or 10/100, which is the same as 1/10, or 0.1.

Let´s convert a few more percents to decimals.

	50
50 % =		= 0.5
	10

	0.5
0.5 % =		= 0.005
	10

Percent can also be used to compare fractions. It would be difficult to determine if the fraction 48 / 75 is greater or lesser than the fraction 60 / 102. But if we convert these fractions into percents, the comparison of their sizes can be made quite easily. In order to do this, divide the fraction to obtain the decimal, and then multiply the decimal by 100 to obtain the percent.

48
	= 0.64		0.64 x 100 = 64 %
75

60
	= 0.59		0.59 x 100 = 59 %
102

Now it is easy to see that 48 / 75 is a larger fraction than 60 / 102. In general, to calculate a percent, divide the fraction, and then multiply by 100. Let´s try a few examples.

Convert 54 / 270 to a percent.

54
	x 100 = 20 %
270

Convert 0.030 / 27 to a percent.

0.030
	x 100 = 11 %
27

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B. Using Percentage to Find the Part of a Whole:
It is often necessary to calculate the percent of an amount, for instance, sales tax, restaurant tip, or the percent composition of a compound.

Here is an example, what is 15 % of $ 20.00? In percent problems, "of" means multiply, "is" means equals, and "what" is your unknown term (X). Therefore, this question can be written as:

X = 15 % x $ 20.00

Note: To work out the problem, we have to put the percent value in its fraction form, just as we did in the earlier section. Therefore, 15 % expressed as a fraction is 15 / 100. This gives us:

	15
X =		x $ 20.00
	100
= $ 3.00

Let´s try another example. What is 6 % of 90 miles? Don´t forget to change the percent to a fraction. We then have:

	6
X =		x 90 miles
	100
= 5.4 miles

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C. Calculating Percents:
In some situations we know the total amount and the part. With this information, we can easily calculate the percent of the part in the whole. In general percents are calculated from the equation:

	Part
Percent =		x 100 %
	Whole

Let´s try an example. 120 is what percent of 800 ?

	120
Percent =		x 100 %
	800
= 15 %

Here´s another example. If 50 grams of water contain 5.5 grams of hydrogen, what is the percent of hydrogen in water?

	5.5 g
Percent =		x 100 %
	50 g
= 11 %

Try the following calculation.

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