GRE Math : Proportion / Ratio / Rate

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #6 : How To Express A Fraction As A Ratio

If \(\displaystyle 3\) apples equal \(\displaystyle 2\) bananas and \(\displaystyle 3\) bananas equal \(\displaystyle 4\) carrots, what is the ratio of an apple to a carrot?

Possible Answers:

\(\displaystyle 9:8\)

\(\displaystyle 8:9\)

\(\displaystyle 2:3\)

\(\displaystyle 3:4\)

\(\displaystyle 4:3\)

Correct answer:

\(\displaystyle 9:8\)

Explanation:

To get the apple to carrot ratio, we need to equal out the bananas. The least common denominator of \(\displaystyle 2\) and \(\displaystyle 3\) is \(\displaystyle 6\). So if \(\displaystyle 3\) apples equal \(\displaystyle 2\) bananas, then \(\displaystyle 6\) bananas equal \(\displaystyle 9\) apples. Also, if \(\displaystyle 3\) bananas equal \(\displaystyle 4\) carrots, then \(\displaystyle 6\) bananas equal \(\displaystyle 8\) carrots. Since now the total bananas are equal, we can find the ratio of apples to carrots. We have \(\displaystyle 9:8\) as the final answer.

Example Question #143 : Fractions

Convert \(\displaystyle 0.57:0.95\) into reduced fraction form.

Possible Answers:

\(\displaystyle \frac{95}{57}\)

\(\displaystyle \frac{3}{8}\)

\(\displaystyle \frac{3}{5}\)

\(\displaystyle \frac{5}{3}\)

\(\displaystyle \frac{57}{95}\)

Correct answer:

\(\displaystyle \frac{3}{5}\)

Explanation:

We can rewrite the ratio \(\displaystyle 0.57:0.95\) as a fraction. The first number in the ratio is in the numerator while the second number in the ratio is in the denominator.

\(\displaystyle \frac{0.57}{0.95}=\frac{57}{95}=\frac{3}{5}\) Remember to get rid of decimals, we can move the decimal point two places to the right. Afterwards, the two numbers are divisible by \(\displaystyle 19\).

Example Question #563 : Arithmetic

Express \(\displaystyle \frac{1}{2}:\frac{1}{3}\) as an integer ratio.

 

Possible Answers:

\(\displaystyle 1:1\)

\(\displaystyle 2:3\)

\(\displaystyle 5:6\)

\(\displaystyle 0.5:0.333\)

\(\displaystyle 3:2\)

Correct answer:

\(\displaystyle 3:2\)

Explanation:

To find an integer ratio, let's find the fractions with a common denominator. This will be \(\displaystyle 6\). Then, we multiply the left by \(\displaystyle 3\) and the right by \(\displaystyle 2\) to get fractions of \(\displaystyle \frac{3}{6}\) and \(\displaystyle \frac{2}{6}\). With the same denominators, we just have numerators to compare. Ratio is then \(\displaystyle 3:2\).

Example Question #564 : Arithmetic

If the ratio of girls to boys is \(\displaystyle 7:6\), what could be the number of children in the class?

Possible Answers:

\(\displaystyle 36\)

\(\displaystyle 40\)

\(\displaystyle 42\)

\(\displaystyle 37\)

\(\displaystyle 39\)

Correct answer:

\(\displaystyle 39\)

Explanation:

If there are \(\displaystyle 7\) girls and \(\displaystyle 6\) boys, that means we have \(\displaystyle 13\) students in the class. To continue to have this ratio, we need an answer than is a multiple of \(\displaystyle 13\)

\(\displaystyle 39\) is a multiple of \(\displaystyle 13\) which is the right answer.

Example Question #565 : Arithmetic

An espresso drink has a ratio of \(\displaystyle 3:7\) ounces of espresso to water. If Amanda wants her drink to be \(\displaystyle 25\%\) espresso, how much water was added?

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle 4\)

\(\displaystyle 3\)

\(\displaystyle 5\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 2\)

Explanation:

In the problem, the drink is \(\displaystyle 30\%\) espresso since the overall weight of the drink is \(\displaystyle 10\) ounces. If we are reducing the concentration of espresso to \(\displaystyle 25\%\), then we can create an equation to figure out the addition of water.

\(\displaystyle \frac{3}{10+x}=\frac{1}{4}\) \(\displaystyle x\) represents the addition of water.

Cross-multiply.

\(\displaystyle 12=10+x\) 

Subtract \(\displaystyle 10\) on both sides. 

\(\displaystyle x=2\)

Example Question #566 : Arithmetic

If Jill, Jack and John found \(\displaystyle \$1000\) and decided to split it \(\displaystyle 6:9:5\) respectively, how much more did Jack get than John?

Possible Answers:

\(\displaystyle 150\)

\(\displaystyle 250\)

\(\displaystyle 200\)

\(\displaystyle 300\)

\(\displaystyle 450\)

Correct answer:

\(\displaystyle 200\)

Explanation:

If Jill, Jack and John get \(\displaystyle 6:9:5\), that means there are \(\displaystyle 20\) parts.

Because they found \(\displaystyle 1000\), each part gets \(\displaystyle \frac{1000}{20}\) or \(\displaystyle \$50\).

Jack gets \(\displaystyle 50\cdot9\) or \(\displaystyle \$450\).

John gets \(\displaystyle 50\cdot5\) or \(\displaystyle \$250\).

Since the question is asking how much more did Jack get than John, we subtract \(\displaystyle 450\) and \(\displaystyle 250\) to get \(\displaystyle 200\).

Example Question #567 : Arithmetic

If there are \(\displaystyle 500\) dolls and \(\displaystyle 96\%\) of them are not broken, what's the ratio of broken dolls to unbroken dolls?

Possible Answers:

\(\displaystyle 24:25\)

\(\displaystyle 1:24\)

\(\displaystyle 25:1\)

\(\displaystyle 1:25\)

\(\displaystyle 24:1\)

Correct answer:

\(\displaystyle 1:24\)

Explanation:

You don't need to solve for the actual number of broken or unbroken dolls. Instead, put the percentages in the ratio because no matter what, the percentages are fixed regardless of amount of dolls broken or unbroken.

So the question is asking for broken to unbroken. The percentage of broken dolls is \(\displaystyle 4\%\).

So we have a ratio of \(\displaystyle 4:96\) or \(\displaystyle 1:24\)

Example Question #11 : How To Express A Fraction As A Ratio

A pot has a ratio of \(\displaystyle 6\) ounces sugar to \(\displaystyle 18\) ounces of water. If I add \(\displaystyle 4\) ounces of sugar to the pot, what percentage of the pot is now sugar?

Possible Answers:

\(\displaystyle 35.7\)

\(\displaystyle 25\)

\(\displaystyle 55.6\)

\(\displaystyle 27.3\)

\(\displaystyle 45.5\)

Correct answer:

\(\displaystyle 35.7\)

Explanation:

We need to understand that there is a total of \(\displaystyle 24\) ounces of solution in a pot. Out of that solution, \(\displaystyle 6\) ounces is sugar. If we add \(\displaystyle 4\) ounces of sugar, we are also changing the volume of the pot. There is a total of \(\displaystyle 10\) ounces of sugar and a total volume of \(\displaystyle 28\) ounces.

To find percentage, we do \(\displaystyle \frac{10}{28}\cdot 100\%\) which is \(\displaystyle 35.7\%\).

Example Question #12 : How To Express A Fraction As A Ratio

Abe, Bob, and Carol went to lunch together and their total bill was 60 dollars. They first decided to split the bill \(\displaystyle 3:2:1\), respectively. Unfortunately, Abe was short on cash and they decided to split the bill \(\displaystyle 2:3:5\). How much more did Carol have to spend on the under the new system of splitting the bill?

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 10\)

\(\displaystyle 30\)

\(\displaystyle 18\)

\(\displaystyle 20\)

Correct answer:

\(\displaystyle 20\)

Explanation:

Since the problem is focusing on Carol, we will only worry about Carol's contribution to the bill.

The original split on the bill was \(\displaystyle 3:2:1\) with Carol paying the smaller portion. With \(\displaystyle 6\) parts, each one was \(\displaystyle \$10\). This was originally the amount Carol was responsible for.

With the the ratio of \(\displaystyle 2:3:5\), this meant there are \(\displaystyle 10\) parts with each being \(\displaystyle \$6\). Carol pays instead \(\displaystyle \$30\).

The difference is then \(\displaystyle 30-10\) or \(\displaystyle \$20\)

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