How to find the whole from the part with percentage - ISEE Middle Level Math

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Question

Pie_graph

Refer to the above diagram. If there were 15,934 voters who were affiliated with a political party in Smith County in 2009, how many voters (nearest whole number) were there total?

Answer

40% of the voters were registered as independents, so 60% were registered as a member of a political party. Since 60% of the voters numbered 15,934, we can find the total number of voters by setting up and solving a proportion:

which rounds to 26,557 voters.

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Question

Pie_graph

Refer to the above graph. If there were 17,856 registered voters in Smith County in 2009, how many voters were registered as neither Republicans nor Democrats (nearest whole number)?

Answer

2% of the voters were registered as members of other parties, and 40% were unaffiliated, so we want to calculate 42% of 17,856, or, equivalently,

which, to the nearest whole number, rounds to 7,500 voters.

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Question

If sales tax on a pair of jeans is , and the jeans cost before tax, what is the final price of the jeans including tax?

Answer

Since the jeans are the only item being purchased, and they cost $, we must first find % of $. In order to do that we multiply $ by the decimal form of %, which is .

Note: In order to find the decimal form of a percent, we divide it by .

Find the tax:

Therefore the sales tax added to the original price is $.

The final cost of the jeans is $.

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Question

For her birthday, Susan asks her mother to buy her a car. Susan’s mother agrees to give Susan 150 percent of whatever amount Susan can save up in six months. If Susan saves , how much does Susan’s mother owe her?

Answer

When Susan's mother agreed to match her savings plus fifty percent, she agreed to give Susan % plus %.

Before multiplying by the amount Susan saved, we must convert % to a decimal by dividing by .

Now we multiply time $.

Susan's mother owes her $.

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Question

240 is 30% of what number?

Answer

Set up the proportion statement and solve for :

Cross-multiply:

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Question

420 is 150% of what number?

Answer

Set up the proportion statement and solve for by cross-multiplying:

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Question

70 is of what number?

Answer

Set up the proportion statement and solve for by cross-multiplying:

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Question

24 is 25% of what number?

Answer

Think is of .

So:

and .

We have:

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Question

Julie bought some groceries at the store where she works for $196.57. She got an employee discount of 15%. How much would the same groceries cost a non-employee?

Answer

Paying at a 15% discount is equvalent to paying 85% of the original price, so $196.57 is 85% of the original (non-employee) price, or, equivalently, 0.85 times that price. If is that price, then we can set up and solve the equation:

A non-employee would pay $231.26 for the groceries.

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Question

Becky ate of a batch of cupcakes. She ate cupcakes. How many cupcakes were there in total?

Answer

This can be solved using a proportion:

Cross multiply and solve for :

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Question

At a pet store, there are 12 dogs and 8 cats. The following week, the number of dogs increases by 25%, while the number of cats decreases by 25%. What is the total number of animals at the store the following week?

Assume the store only sells dogs and cats.

Answer

If the population of dogs increases by 25%, then we first find 25% of 12 (which is 3) and add the 3 to 12. This gives us 15 dogs.

If the population of cats decreases by 25%, then we find 25% of 8 (which is 2), and subtract if from 8. This gives us 6.

Now that we know the final individual numbers of dogs and cats, we can add them to find the final answer.

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Question

10 percent of a cake weights 20 ounces. The entire cake is cut into 8 pieces. How many ounces does each piece weigh?

Answer

If 10 percent of the cake weights 20 ounces, then the entire cake will weigh 200 ounces, because 10 times 20 is 200.

If the cake has 8 slices, then each slice will weigh (in ounces) 200 divided by 8. 200 divided by 8 is 25; therefore, 25 ounces is the correct answer.

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Question

Tom the baker made blueberry muffins on Tuesday, and Stan the baker made and muffins that day. On Wednesday, each baker decided to increase his production of blueberry muffins by . What is the average of blueberry muffins that Tom and Stan baked on Wednesday?

Answer

Tom made blueberry muffins on Tuesday, and Stan made and muffins that day. On Wednesday, each baker decided to increase his production of blueberry muffins by .

Given that of is , the number of muffins made by Tom on Wednesday would be .

Given that of is , the number of muffins made by Stan on Wednesday would be .

The average is calculated by adding numbers in a list together, and then dividing by the number of items in that list. This gives us:

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Question

There are 12 sopranos in the Red Street Choir. If sopranos are 40% of the choir, how many total members make up the Red Street Choir?

Answer

When given a part, you can use a percentage to determine the whole by converting the percentage to a decimal and dividing the part by that number.

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Question

If you have of a quiz completed after questions, how long is the quiz?

Answer

To find a part of a whole with a percentage, you multiply the whole by the percent.

To find the opposite, you divide the part by the percent so it would be .

This is equal to

or .

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Question

There are 8 pieces of pizza. If Justin at 25% of the pizza, how many pieces did he have?

Answer

25% is equivalent to the fraction

and can then be reduced to

which is equivalent to

,

meaning that if Justin ate 25% of the pizza, he ate 2 of the 8 pieces.

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