Percent sign

To change a fraction to a percentage, divide the denominator by the numerator and multiply the results (quotient) by 100 and then add a percent sign (%). 

To convert the percentage of a number to equivalent decimal fraction, first drop the percent sign and then divide the numerator by 100. 

To remember the space, treat units like words. You would write twelve compounds not twelvecompounds hence, you would write 12 mh not 12mL. A notable exception to this rule occurs with percentages in this case, there is no space between the number and the percent sign (%) ... 

Leave a space between a numeral and its unit of measure, unless the unit of measure is a percent sign (%) ... 

To write a fraction as a decimal, you divide the numerator by the denominator, inserting the decimal point where needed. To change a decimal to a percent, you move the decimal point two places to the right and use a percent sign (%). 

To change a percent to a decimal, drop off the percent sign and move the decimal point two places to the left. If there aren t enough places to move the decimal point, add zeros on the left before moving the decimal point. 

To change a percent to a fraction, remove the percent sign and write the number over 100. Then reduce if possible. Example Change 4% to a fraction. 

Mathematical operations have specific rules for the use of mathematical symbols with SI units. A space or a half-high dot represents the multiplication of units a negative exponent, horizontal line, or slash represents the division of units, and if these mathematical symbols appear in the same line, parentheses must differentiate them. The percent sign (%) denotes the number 0.01 or 1/100, so that 1%= 0.01, 30% = 0.30, and so forth. Arabic numerals with the appropriate SI or recognized unit indicate the values of quantities. Commas are not used to separate numbers into groups of three. If more than four digits appear on either side of the decimal point, a space Table 3. Prefixes. separates the groups of three. 

Move the decimal point two places to the right and add the percent sign 0.72 = 72%. 

In other words, 15, our new number, is what we have after taking 10% of an original number. We can find the original number by working backward. First, write 10% as a decimal. Move the decimal point two places to the left and remove the percent sign 10% = 0.10. 

In Chapter 9, we learned that we could write a decimal as a percent by moving the decimal point of a number two places to the right and adding the percent sign (%). 

Both numbers have the same digits in the ones, tenths, and hundredths places, but they have different digits in the thousandths place, so these numbers are not equal. Convert 71.88% to a decimal. Remove the percent sign and shift the decimal point two places to the left. 71.88% = 0.7188, which is equal to the given decimal. For more on this concept, see Chapter 11. 

When concentration is given as percentage, use the percent sign closed up to the number. 

Assume a 100-gram sample. This will allow the percent signs to be written as grams. ... 

You are given the percent composition of methyi acetate and must find the empiricai formuia. Because you can assume that each percent by mass represents the mass of the eiement in a 100.00-g sam-pie, the percent sign can be repiaced with the unit grams. Then, you can convert from grams to moies using the moiar mass and find the smaiiest whoie-number ratio of moies of the eiements. 

---