Basic Arithmetic : Percents and Decimals
Study concepts, example questions & explanations for Basic Arithmetic
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Example Questions
Example Question #1 : Increase
In 2012, a university received 150,249 applicants. In 2013, the same university received 190,201 applicants. By what percent did the total number of applicants increase from 2012 to 2013?
To find the percent change, use the following formula:
Our new number of applicants is 190,201, while the original number of applicants is 150,249.
Example Question #1 : Increase
In January, Widget Company made 
To find the percent increase, use the following formula:
In the case of Widget Company,
Therefore, the percent increase is
Example Question #1 : Increase
Derek ran his first mile in 
What is the percent increase between the time it took Derek to run the first and second mile?
The correct answer is a percent change (increase) of 
This can be calculated using the following equation:
Therefore, the answer is a percent increase of 
Example Question #1 : Finding Percent Change
In May of the past year, Harry's company made 
To find percent change, use the following formula:
Our new value is the profit in June, $210,219. Our old value is the profit in May, $189,281.
Example Question #1 : Decrease
In March, an athlete weighed 
The formula to find percentage change is
So for our athlete, our new weight is 170 pounds, and the original weight is 195 pounds.
Because the question already tells us that we need to find the percent lost, or percent decrease, we can drop the negative sign in the answer.
Example Question #2 : Finding Percent Change
Last month the shirt you wanted to buy cost 
1. Subtract the lower price from the higher price.
2. Divide the difference or amount of change by the initial price:
or 10% price decrease
Example Question #3 : Finding Percent Change
We first find 18% of 76:
Since 76 is being decreased by this amount, we subtract 13.68:
Example Question #1 : Finding Percent Change
At age 
The questions throws a lot of numbers at us, but the only ones we are concerned with are those having to do with height. We use the following formula:
We want to know the percent change. We know the amount change, 6 inches, and the original amount, 52 inches. Plugging these into the formula, we get:
Rounding this number to the nearest tenth gives us 11.5%.
Example Question #1 : Finding Percent Change
Percent change is found by the following formula:
Amount change is the difference between the old amount and the new amount.
Here, the original amount is 30, and the new amount is 27. The difference between them is:
We plug in 3 for amount change and 30 for original amount and simplify:
Our final answer is 10%.
Example Question #1 : Creating Linear Equations With Part, Percent, And Whole
What is the perimeter of a semicircle with an area of 
This is a multi-step problem. The perimeter of a semicircle is the sum of the circumference and diameter. First, since we are given the area, we will need to find the radius.
For the area of a semicircle:
Since the area is 
Since the radius is 2, the diameter is 4.
The circumference for a semicircle is:
The perimeter is the sum of the circumference and diameter:
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