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Can you explain to me how to find the percent of change? And help me with this problem?

On Monday,my math class learned how to find the percent of change, and I was absent on Monday. And we did some problems in class today, and I still don't understand it.

Can you help me to understand/explain to me the percent of change?

Also, can you help me with this word problem:

According to the United States Census Bureau, the United States population was projected to be about 294,000,000 people on July 1, 2004. The two most populous states were California, with a population of about 36,000,000, and Texas, with a population of about 23,000,000. About what percent of the United States population lived in California of Texas? Round your answer to the nearest percent?

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2 Answers

If the new value is Y, and the old value is X then the percent change is [(Y - X) / X] * 100%

Here is an example:

Q: The population of squirrels in Greenville was 50000. After a year, the population grew to 52000. By what percent did the population of squirrels in Greenville grow?

A: [(52000 - 50000) / 50000] * 100% = [2000 / 50000] * 100% = 0.04*100% = 4%.

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For the other question, if the number of items in total is Y, and the number if items satisfying a given criterion is X, then the percent of items with the criterion is (X / Y) * 100%.

In your question, the total population in California and Texas combined was

36,000,000 + 23,000,000 = 59,000,000.

The total population in the U.S. was 294,000,000 as given in the problem.

The percent living in these two states then is

(59,000,000 / 294,000,000) * 100% = 20%

 

To solve a problem about percent of change, you need to divide the amount of change by the original amount.  To find the amount of change, subtract the initial amount from the final amount.  The formula for percent of change can be written:


Percent of Change = (Final amount - Initial amount)/Initial amount


For example, If you start with 100 and end with 120, you would write:

Percent of change = (120 - 100)/100

Percent of change = 20/100

Percent of change = .2

Since you want a percent, you need to change the decimal to a percent.  To do this, move the decmial place 2 places to the right and add a percent sign.

Percent of change = 20%

Additional Word Problem:

This problme is not a percent change problem.  It is just a percentage problem.  You need to add the population of the two states together, and then divide that number by the total population of the US.

(36,000,000 + 23,000,000)/294,000,000

59,000,000/294,000,000

We can divide both the numerator and denominator by 1,000,000 to simplify the fraction:

59/294

The answer is approximately .20068027.  Converted to a percentage, we have:

20.068027%

Rounded to the nearest percent, the answer is 20%.

 

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