Algebra 1 : How to find the percent of decrease

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #21 : How To Find The Percent Of Decrease

Kerri wanted to make a chart to calculate how much time she was spending on studying for her tests. For her midterm, she charted that she spent 1 hour and 30 minutes studying every day for three days. Since she was grasping the material, for the final exam Kerri only studied 3 hours total. What is the percent change for the amount of time studying between the midterm and final exam?

Possible Answers:

Correct answer:

Explanation:

The first task to do in this problem is to convert the time amounts for studying to either minutes or hours. The problem says Kerri spent three days of studying for 1 hour and 30 minutes each, which is also 1.5 (30 minutes is half an hour) hours. Multiply 3 days by 1.5 hours o get 4.5 hours of total studying for her midterm. Since the final exam is already in the unit of hours the amount of 3 hours is ready to be worked with.

Use the percent change formula new amount subtracted by old amount then divided by the old amount and multiplied by 100 to find the percent change.

Kerri studied 33.33% less for the final exam than she did for the midterm.

Example Question #21 : How To Find The Percent Of Decrease

You decide that 15 pairs of shoes is far too many and sell 8 of them. Your percent decrease in shoes is?

Possible Answers:

None of these.

Correct answer:

Explanation:

Subtract the new value from the old value:

Divide by the original number:

Multiply by 100:

A 47% decrease in shoes.

Example Question #21 : How To Find The Percent Of Decrease

Last week, a case of water cost $4.00.  This week, it is on sale for $3.00 a case.  Find the percent decrease.

Possible Answers:

Correct answer:

Explanation:

To find the percent decrease, we will use the following formula:

Example Question #22 : How To Find The Percent Of Decrease

Yesterday, chicken cost $4 a pound.  Today, it costs $3.50 a pound.  Find the percent decrease.

Possible Answers:

Correct answer:

Explanation:

To find the percent decrease, we will use the following formula:

Example Question #133 : Percent Of Change

Last week, a shirt cost $25.  This week, it is on sale for $10.  Find the percent decrease.

Possible Answers:

Correct answer:

Explanation:

To find the percent decrease, we use the following formula:

 

Therefore, the percent decrease of the shirt is 60%.

Example Question #134 : Percent Of Change

A tennis player won 25 of her 35 matches in the fall season. In the spring season, she won 23 of her 35 matches. What was the tennis player's percent change in the number of games she won from fall to spring?

Possible Answers:

Correct answer:

Explanation:

In this question, it is important to not be confused by the total amount of games number. Since the number of games is the same, you can just take the new amount of wins subtracted by the old amount of wins then divide by the old amount and multiply by 100.

The amount of games the tennis player won decreased by 8% from the fall season to the spring season.

Example Question #131 : Percent Of Change

Your weekly allowance went from $40 to $30 a week.  Find the percent decrease in your allowance.

Possible Answers:

Correct answer:

Explanation:

To find percent decrease, we use the following formula:

 

Using the information given, we know the following:

so we can substitute these values into the formula.  We get

 

 

Therefore, the percent decrease in your allowance is .

Example Question #21 : How To Find The Percent Of Decrease

In 2013, a water tower contained 950,000 gallons. By 2014, the tower only contained 860,000 gallons of water. What was the percentage change in the amount of water that the tower contained? (Round to one decimal place)

Possible Answers:

Correct answer:

Explanation:

Use the formula new amount subtracted by old amount then divided by the old amount and multiplied by 100. The new amount in this case is 860,000 and the old amount is 950,000.

The amount of water in the tower decreased by 9.5%

Example Question #21 : How To Find The Percent Of Decrease

When performing a Google search for "Lions" the amount of search results are 257 million. After refining the search to "African Lions" the amount of search results is 6.7 million. What is the percentage change by going from a search for "Lions" to "African Lions"? (Round the answer to one decimal place)

Possible Answers:

Correct answer:

Explanation:

The percent change formula new amount subtracted by old amount then divided by old amount and multiplied by 100 should be used for this problem. The new amount is 6.7 million and the old amount is 257 million. It is not necessary to use the expanded numbers 6,700,000 or 257,000,000 to work out the problem but it will also work.

By refining the search, the amount of search results fell by 97.4%

Example Question #21 : How To Find The Percent Of Decrease

A closet contains 250 shoes. During spring cleaning, the owner decides to donate away 50 of those shoes. What is the percentage change in the amount of shoes the person owns?

Possible Answers:

Correct answer:

Explanation:

Use the percentage change formula new amount subtracted by old amount then divided by old amount and multiplied by 100. It is important in this question to realize what the new and old amount are. The old amount is 250 shoes. The new amount is 250 less the 50 shoes so 200. The formula should be

The amount of shoes owned decreased by 20%.

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