Common Core: 7th Grade Math : Decide if Two Quantiies are in a Proportional Relationship: CCSS.Math.Content.7.RP.A.2a

Study concepts, example questions & explanations for Common Core: 7th Grade Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Proportion / Ratio / Rate

In a class of \(\displaystyle 60\) students, the ratio of freshmen to sophomores to juniors is \(\displaystyle 2:3:5\). How many juniors are in the class?

Possible Answers:

\(\displaystyle 18\)

\(\displaystyle 12\)

\(\displaystyle 15\)

\(\displaystyle 30\)

Correct answer:

\(\displaystyle 30\)

Explanation:

Let \(\displaystyle 2x\) be the number of freshmen, \(\displaystyle 3x\) be the number of sophomores, and \(\displaystyle 5x\) be the number of juniors.

Now, since we have \(\displaystyle 60\) students,

\(\displaystyle 2x+3x+5x=60\)

\(\displaystyle 10x=60\)

\(\displaystyle x=6\)

Since we want to find the number of juniors, we need to find the value of \(\displaystyle 5x\).

\(\displaystyle 5x=5(6)=30\)

Example Question #81 : Ratios & Proportional Relationships

In a zoo with \(\displaystyle 200\) animals, the ratio of mammals to reptiles to birds is \(\displaystyle 5:6:9\). How many birds does the zoo have?

Possible Answers:

\(\displaystyle 90\)

\(\displaystyle 100\)

\(\displaystyle 50\)

\(\displaystyle 60\)

Correct answer:

\(\displaystyle 90\)

Explanation:

Let \(\displaystyle 5x\) be the number of mammals,\(\displaystyle 6x\) be the number of reptiles, and \(\displaystyle 9x\) be the number of birds.

Since the zoo has \(\displaystyle 200\) animals,

\(\displaystyle 5x+6x+9x=200\)

\(\displaystyle 20x=200\)

\(\displaystyle x=10\)

Because we want the number of birds, we need to find the value of \(\displaystyle 9x\).

\(\displaystyle 9x=9(10)=90\)

Example Question #2 : Proportion / Ratio / Rate

In a high school of \(\displaystyle 2000\) students, the ratio of freshmen to sophomores to juniors to seniors is \(\displaystyle 2:3:8:12\). How many juniors does this high school have?

Possible Answers:

\(\displaystyle 800\)

\(\displaystyle 960\)

\(\displaystyle 500\)

\(\displaystyle 640\)

Correct answer:

\(\displaystyle 640\)

Explanation:

Let \(\displaystyle 2x\) be the number of freshmen, \(\displaystyle 3x\) be the number of sophomores, \(\displaystyle 8x\) be the number of juniors, and \(\displaystyle 12x\) be the number of seniors.

Because the high school has \(\displaystyle 2000\) students,

\(\displaystyle 2x+3x+8x+12x=2000\)

\(\displaystyle 25x=2000\)

\(\displaystyle x=80\)

Since we want to find out how many juniors there are, we need the value of \(\displaystyle 8x\).

\(\displaystyle 8x=80\times8=640\)

Example Question #61 : Number Concepts And Operations

In a high school, the ratio of freshmen to seniors is \(\displaystyle 4:5\). If there are \(\displaystyle 150\) seniors, how many freshmen are there?

Possible Answers:

\(\displaystyle 120\)

\(\displaystyle 110\)

\(\displaystyle 100\)

\(\displaystyle 180\)

Correct answer:

\(\displaystyle 120\)

Explanation:

Set up the following proportion, with \(\displaystyle x\) being the number of freshmen.

\(\displaystyle \frac{4}{5}=\frac{x}{150}\)

Now, cross-multiply and solve for \(\displaystyle x\).

\(\displaystyle 5x=600\)

\(\displaystyle x=120\)

Example Question #3 : Proportion / Ratio / Rate

On a beach, the ratio of crabs to seagulls is \(\displaystyle 9:5\). If there are \(\displaystyle 182\) crabs and seagulls on the beach, how many crabs are there?

Possible Answers:

\(\displaystyle 38\)

\(\displaystyle 109\)

\(\displaystyle 114\)

\(\displaystyle 117\)

Correct answer:

\(\displaystyle 117\)

Explanation:

Let \(\displaystyle 9x\) be the number of crabs and \(\displaystyle 5x\) be the number of seagulls.

Since there are \(\displaystyle 182\) crabs and seagulls on the beach,

\(\displaystyle 9x+5x=182\)

\(\displaystyle 14x=182\)

\(\displaystyle x=13\)

Because the question asks for the number of crabs, we need to find the value of \(\displaystyle 9x\).

\(\displaystyle 9x=13\times9=117\)

Example Question #1 : Fractions

There are \(\displaystyle 45\) boys and \(\displaystyle 36\) girls at a playground. What is the ratio of boys to girls?

Possible Answers:

\(\displaystyle 5:4\)

\(\displaystyle 4:3\)

\(\displaystyle 4:5\)

\(\displaystyle 3:4\)

Correct answer:

\(\displaystyle 5:4\)

Explanation:

Write the numbers of boys and girls as a fraction, then simplify.

\(\displaystyle \frac{45}{36}=\frac{5}{4}\)

\(\displaystyle \frac{5}{4}\) can also be written as \(\displaystyle 5:4\)

Example Question #62 : Number Concepts And Operations

At a high school, there are \(\displaystyle 36\) freshmen, \(\displaystyle 42\) sophomores, \(\displaystyle 24\) juniors, and \(\displaystyle 30\) seniors. What is the ratio of seniors to freshmen?

Possible Answers:

\(\displaystyle 5\) to \(\displaystyle 6\)

\(\displaystyle 7\) to \(\displaystyle 6\)

\(\displaystyle 6\) to \(\displaystyle 5\)

\(\displaystyle 2\) to \(\displaystyle 3\)

Correct answer:

\(\displaystyle 5\) to \(\displaystyle 6\)

Explanation:

Write the number of seniors and numbers of freshmen as a fraction:

\(\displaystyle \frac{30}{36}=\frac{5}{6}\)

That fraction is equivalent to \(\displaystyle 5\text{ to }6\).

Example Question #4 : Proportion / Ratio / Rate

The angles in a triangle are in the ratio \(\displaystyle 1:3:6\). What is the angle measurement of the largest angle?

Possible Answers:

\(\displaystyle 100^{\circ}\)

\(\displaystyle 108^{\circ}\)

\(\displaystyle 98^{\circ}\)

\(\displaystyle 54^{\circ}\)

Correct answer:

\(\displaystyle 108^{\circ}\)

Explanation:

Let \(\displaystyle x, 3x, \text{ and }6x\) be the values of the angles.

Since all the angles in a triangle need to add up to \(\displaystyle 180\),

\(\displaystyle x+3x+6x=180\)

\(\displaystyle 10x=180\)

\(\displaystyle x=18\)

Because we want the value of the largest angle, we need to find the value of \(\displaystyle 6x\).

\(\displaystyle 6x=18(6)=108\)

Example Question #14 : Fractions

John and Michela are business partners who agreed to split profits at a ratio of 2:3, with Michela taking the larger share. If their business made \(\displaystyle \$36\textup{,}000\) in the first year, how much money did Michela make?

Possible Answers:

\(\displaystyle \$22\textup{,}200\)

\(\displaystyle \$14\textup{,}400\)

\(\displaystyle \$18\textup{,}600\)

\(\displaystyle \$21\textup{,}600\)

Correct answer:

\(\displaystyle \$21\textup{,}600\)

Explanation:

Let \(\displaystyle 2x\) be the amount John takes home and \(\displaystyle 3x\) be the amount Michela takes home.

Since their business made \(\displaystyle \$36,000\),

\(\displaystyle 2x+3x=36000\)

\(\displaystyle 5x=36000\)

\(\displaystyle x=7200\)

We want to know how much Michela made so we need to find the value of \(\displaystyle 3x\).

\(\displaystyle 3x=7200\times3=21600\)

Example Question #11 : Fractions

The angles in a triangle have a ratio of \(\displaystyle 3:4:5\). What is the measurement of the smallest angle?

Possible Answers:

\(\displaystyle 35^{\circ}\)

\(\displaystyle 45^{\circ}\)

\(\displaystyle 105^{\circ}\)

\(\displaystyle 55^{\circ}\)

Correct answer:

\(\displaystyle 45^{\circ}\)

Explanation:

Let \(\displaystyle 3x, 4x,\text{ and}, 5x\) be the values of the angles.

Since there are \(\displaystyle 180\) degrees in a triangle,

\(\displaystyle 3x+4x+5x=180\)

\(\displaystyle 12x=180\)

\(\displaystyle x=15\)

Since we want the value of the smallest angle, find the value of \(\displaystyle 3x\).

\(\displaystyle 3x=15\times3=45\)

Learning Tools by Varsity Tutors