Basic Arithmetic : Percents and Decimals

Study concepts, example questions & explanations for Basic Arithmetic

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Example Questions

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Example Question #1 : Percents And Decimals

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?

Possible Answers:

Correct answer:

Explanation:

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 : Percents And Decimals

In January, Widget Company made , widgets. In February, the same company made , widgets. By what percentage did the amount of widgets made increase?

Possible Answers:

Correct answer:

Explanation:

To find the percent increase, use the following formula:

In the case of Widget Company,

Therefore, the percent increase is 

Example Question #1 : Percents And Decimals

Derek ran his first mile in  minutes and his second mile in  minutes. 

What is the percent increase between the time it took Derek to run the first and second mile?

Possible Answers:

Correct answer:

Explanation:

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 #72 : Basic Arithmetic

In May of the past year, Harry's company made  in profit, and in June of that same year, his company made  in profit. By what percent did his profit increase from May to June?

Possible Answers:

Correct answer:

Explanation:

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  pounds. In April, the same athlete weighed  pounds. What is the athlete's percentage of weight loss?

Possible Answers:

Correct answer:

Explanation:

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 #1 : Decrease

Last month the shirt you wanted to buy cost  and this month it costs . What is the percent decrease?

Possible Answers:

Correct answer:

Explanation:

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 #1 : Decrease

 is decreased by . What is the new number?

Possible Answers:

Correct answer:

Explanation:

We first find 18% of 76:

Since 76 is being decreased by this amount, we subtract 13.68:

Example Question #1 : Percents And Decimals

At age  you are  inches taller than you were  years ago, when you were  inches tall. What is the percent change in your height from  years ago to now? Round your answer to the nearest tenth.

Possible Answers:

Correct answer:

Explanation:

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

 is decreased to . What is the percent change?

Possible Answers:

Correct answer:

Explanation:

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 : Finding Part, Percent, And Whole

What is the perimeter of a semicircle with an area of ?

Possible Answers:

Correct answer:

Explanation:

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 , substitute this into A to find radius r.

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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