# 8.1.12 To Write One Number as a Percentage of Another

[ Source: U.S. Census (state data, “Search”; national data, “Map”) ]

## Activity: Writing One Number as a Percentage of Another

(a) In 2010, the population of Maryland was about 5,774,000, and the total population of the United States was about 308,746,000. What was the population of Maryland as a percentage of the total population of the United States? ### Comment

To find the percentage, you take the ratio of “part to whole” and multiply by 100%. (a) The calculation required is .

Try this on the calculator. The calculator should show: You need to round the answer. How many decimal places would make sense here?

This rather depends on who the answer is for. Probably, either one or two decimal places are sufficient. Round the answer to 2 decimal places.

Rounded to 2 decimal places, the population of Maryland was 1.87% of the total population of the United States in 2010.

(b) California has the largest population of any state in the US, about 37,254,000 in 2010 and the total population of the United States was about 308,746,000. Find the population of California as a percentage of the total population of the United States, rounding your answer to 2 decimal places. ### Comment

Write the part divided by the whole, then multiply by 100%. (b) The calculator shows: The population of California, rounded to 2 decimal places, was about 12.07% of the total population of the United States in 2010.

## To recap:

• To find a percentage of a number, write the percentage as a fraction (by dividing by 100) and multiply by the number. Or use the percent key, by entering the percentage followed by the percent key and multiply by the number.
• To write one number as a percentage of another, write the part divided by the whole and multiply by 100%.

References

U.S. Census Bureau. “2010 Census Interactive Population Map.” U.S. Census Bureau. http://2010.census.gov/ 2010census/ popmap/ index.php [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]

U.S. Census Bureau. “2010 Census Interactive Population Search.” U.S. Census Bureau. http://2010.census.gov/ 2010census/ popmap/ ipmtext.php

8.1.11 Calculator Exploration: Using Percentages

8.1.13 World Populations