Common Core: 6th Grade Math : Ratios & Proportional Relationships

Study concepts, example questions & explanations for Common Core: 6th Grade Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #71 : Ratios & Proportional Relationships

Red is a very popular car color. A production company manufactures cars and parks them in a lot behind the plant. There are \(\displaystyle 800\) cars in the parking lot and \(\displaystyle 80\%\) of them are red. How many red cars are in the parking lot?

Possible Answers:

\(\displaystyle 460\)

\(\displaystyle 80\)

\(\displaystyle 630\)

\(\displaystyle 640\)

\(\displaystyle 360\)

Correct answer:

\(\displaystyle 640\)

Explanation:

We can use ratios and proportions to solve this problem. Percentages can be written as ratios. The word “percent” means for every hundred. In the problem, we are told that \(\displaystyle 80\%\) of the cars are red. In other words, for every hundred cars \(\displaystyle 80\) of them are red. We can write the following ratio:

\(\displaystyle 80:100\rightarrow\frac{80}{100}\)

Reduce.

\(\displaystyle \frac{80}{100}\rightarrow \frac{8}{10}\rightarrow \frac{4}{5}\)

We know that there are \(\displaystyle 800\) cars in the parking lot. We can write the following ratio by substituting the variable \(\displaystyle Red\) for the number of red cars:

\(\displaystyle Red:800\rightarrow \frac{Red}{800}\)

Now, we can create a proportion using our two ratios.

\(\displaystyle \frac{4}{5}=\frac{Red}{800}\)

Cross multiply and solve for \(\displaystyle Red\).

\(\displaystyle 5 \times Red=4\times800\)

Simplify.

\(\displaystyle 5 Red=3200\)

Divide both sides of the equation by \(\displaystyle 5\).

\(\displaystyle \frac{5Red}{5}=\frac{3200}{5}\)

Solve.

\(\displaystyle Red=640\)

There are \(\displaystyle 640\) red cars in the parking lot.

Example Question #72 : Ratios & Proportional Relationships

Red is a very popular car color. A production company manufactures cars and parks them in a lot behind the plant. There are \(\displaystyle 3200\) cars in the parking lot and \(\displaystyle 8\%\) of them are red. How many red cars are in the parking lot?

Possible Answers:

\(\displaystyle 182\)

\(\displaystyle 218\)

\(\displaystyle 800\)

\(\displaystyle 256\)

\(\displaystyle 188\)

Correct answer:

\(\displaystyle 256\)

Explanation:

We can use ratios and proportions to solve this problem. Percentages can be written as ratios. The word “percent” means for every hundred. In the problem, we are told that \(\displaystyle 8\%\) of the cars are red. In other words, for every hundred cars \(\displaystyle 8\) of them are red. We can write the following ratio:

\(\displaystyle 8:100\rightarrow\frac{8}{100}\)

Reduce.

\(\displaystyle \frac{8}{100}\rightarrow \frac{4}{50}\rightarrow \frac{2}{25}\)

We know that there are \(\displaystyle 3200\) cars in the parking lot. We can write the following ratio by substituting the variable \(\displaystyle Red\) for the number of red cars:

\(\displaystyle Red:3200\rightarrow \frac{Red}{3200}\)

Now, we can create a proportion using our two ratios.

\(\displaystyle \frac{2}{25}=\frac{Red}{3200}\)

Cross multiply and solve for \(\displaystyle Red\).

\(\displaystyle 25 \times Red=2\times3200\)

Simplify.

\(\displaystyle 25 Red=6400\)

Divide both sides of the equation by \(\displaystyle 25\).

\(\displaystyle \frac{25Red}{25}=\frac{6400}{25}\)

Solve.

\(\displaystyle Red=256\)

There are \(\displaystyle 256\) red cars in the parking lot.

Example Question #1 : Solving Word Problems With One Unit Conversion

A carpenter is making a model house and he buys \(\displaystyle 8\ feet\) of crown moulding to use as accent pieces. He needs \(\displaystyle 98\ inches\) of the moulding for the house. How many feet of the material does he need to finish the model?

Possible Answers:

\(\displaystyle 9 \tfrac{5}{6} \ feet\)

\(\displaystyle 8 \tfrac{5}{6} \ feet\)

\(\displaystyle 7 \tfrac{5}{6} \ feet\)

\(\displaystyle 9 \tfrac{1}{6} \ feet\)

\(\displaystyle 8 \tfrac{1}{6} \ feet\)

Correct answer:

\(\displaystyle 8 \tfrac{1}{6} \ feet\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 98\ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 98\ inches:x\ feet\rightarrow \frac{98\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{98\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=98\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=98\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{98}{12}\)

Solve.

\(\displaystyle x=8 \tfrac{2}{12} \ feet\)

Reduce.

\(\displaystyle x=8 \tfrac{1}{6} \ feet\)

The carpenter needs \(\displaystyle 8 \tfrac{1}{6} \ feet\) of material.

Example Question #2 : Solving Word Problems With One Unit Conversion

A carpenter is making a model house and he buys \(\displaystyle 8\ feet\) of crown moulding to use as accent pieces. He needs \(\displaystyle 124\ inches\) of the moulding for the house. How many feet of the material does he need to finish the model?

Possible Answers:

\(\displaystyle 10 \tfrac{1}{3} \ feet\)

\(\displaystyle 9 \tfrac{2}{3} \ feet\)

\(\displaystyle 11 \tfrac{1}{3} \ feet\)

\(\displaystyle 10 \tfrac{3}{5} \ feet\)

\(\displaystyle 10 \tfrac{2}{3} \ feet\)

Correct answer:

\(\displaystyle 10 \tfrac{1}{3} \ feet\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 124\ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 124\ inches:x\ feet\rightarrow \frac{124\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{124\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=124\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=124\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{124}{12}\)

Solve.

\(\displaystyle x=10 \tfrac{4}{12} \ feet\)

Reduce.

\(\displaystyle x=10 \tfrac{1}{3} \ feet\)

The carpenter needs \(\displaystyle 10 \tfrac{1}{3} \ feet\) of material.

Example Question #91 : Ratio And Proportion

A carpenter is making a model house and he buys \(\displaystyle 8\ feet\) of crown moulding to use as accent pieces. He needs \(\displaystyle 39\ inches\) of the moulding for the house. How many feet of the material does he need to finish the model?

Possible Answers:

\(\displaystyle 3 \tfrac{2}{5} \ feet\)

\(\displaystyle 3 \tfrac{1}{5} \ feet\)

\(\displaystyle 3 \tfrac{1}{2} \ feet\)

\(\displaystyle 3 \tfrac{3}{4} \ feet\)

\(\displaystyle 3 \tfrac{1}{4} \ feet\)

Correct answer:

\(\displaystyle 3 \tfrac{1}{4} \ feet\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 39\ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 39\ inches:x\ feet\rightarrow \frac{39\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{39\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=39\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=39\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{39}{12}\)

Solve.

\(\displaystyle x=3 \tfrac{3}{12} \ feet\)

Reduce.

\(\displaystyle x=3 \tfrac{1}{4} \ feet\)

The carpenter needs \(\displaystyle 3 \tfrac{1}{4} \ feet\) of material.

Example Question #2 : Solving Word Problems With One Unit Conversions

A carpenter is making a model house and he buys \(\displaystyle 8\ feet\) of crown moulding to use as accent pieces. He needs \(\displaystyle 87\ inches\) of the moulding for the house. How many feet of the material does he need to finish the model?

Possible Answers:

\(\displaystyle 7 \tfrac{1}{4} \ feet\)

\(\displaystyle 7 \tfrac{2}{5} \ feet\)

\(\displaystyle 6 \tfrac{3}{4} \ feet\)

\(\displaystyle 8 \tfrac{1}{5} \ feet\)

\(\displaystyle 8 \tfrac{1}{4} \ feet\)

Correct answer:

\(\displaystyle 7 \tfrac{1}{4} \ feet\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 87\ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 87\ inches:x\ feet\rightarrow \frac{87\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{87\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=87\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=87\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{87}{12}\)

Solve.

\(\displaystyle x=7 \tfrac{3}{12} \ feet\)

Reduce.

\(\displaystyle x=7 \tfrac{1}{4} \ feet\)

The carpenter needs \(\displaystyle 7 \tfrac{1}{4} \ feet\) of material.

Example Question #1 : Solving Word Problems With One Unit Conversion

A carpenter is making a model house and he buys \(\displaystyle 8\ feet\) of crown moulding to use as accent pieces. He needs \(\displaystyle 144\ inches\) of the moulding for the house. How many additional feet of the material will he need to purchase to finish the model?

Possible Answers:

\(\displaystyle 8\)

\(\displaystyle 6\)

\(\displaystyle 10\)

\(\displaystyle 4\)

\(\displaystyle 2\)

Correct answer:

\(\displaystyle 4\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 144\ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 144\ inches:x\ feet\rightarrow \frac{144\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{144\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=144\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=144\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{144}{12}\)

Solve.

\(\displaystyle x=12 \ feet\)

The carpenter needs \(\displaystyle 12 \ feet\) of material. Since he already has \(\displaystyle 8 feet\) he will need to purchase \(\displaystyle 4\) more to finish the project.

Example Question #1 : Solving Word Problems With One Unit Conversion

A carpenter is making a model house and he buys \(\displaystyle 8\ feet\) of crown moulding to use as accent pieces. He needs \(\displaystyle 164\ inches\) of the moulding for the house. How many feet of the material does he need to finish the model?

Possible Answers:

\(\displaystyle 12 \tfrac{1}{3} \ feet\)

\(\displaystyle 13 \tfrac{1}{5} \ feet\)

\(\displaystyle 11 \tfrac{2}{3} \ feet\)

\(\displaystyle 13 \tfrac{2}{3} \ feet\)

\(\displaystyle 13 \tfrac{1}{3} \ feet\)

Correct answer:

\(\displaystyle 13 \tfrac{2}{3} \ feet\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 164\ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 164\ inches:x\ feet\rightarrow \frac{164\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{164\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=164\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=164\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{164}{12}\)

Solve.

\(\displaystyle x=13 \tfrac{8}{12} \ feet\)

Reduce.

\(\displaystyle x=13 \tfrac{2}{3} \ feet\)

The carpenter needs \(\displaystyle 13 \tfrac{2}{3} \ feet\) of material.

Example Question #2 : Solving Word Problems With One Unit Conversion

A carpenter is making a model house and he buys \(\displaystyle 8\textup{ feet}\) of crown molding to use as accent pieces. He needs \(\displaystyle 18\textup{ inches}\) of the molding for the house. How many feet of the material does he need to finish the model?

Possible Answers:

\(\displaystyle 2 \tfrac{1}{2} \textup{ feet}\)

\(\displaystyle 1 \tfrac{2}{3} \textup{ feet}\)

\(\displaystyle 2 \tfrac{3}{4} \textup{ feet}\)

\(\displaystyle 3 \tfrac{1}{2} \textup{ feet}\)

\(\displaystyle 1 \tfrac{1}{2} \textup{ feet}\)

Correct answer:

\(\displaystyle 1 \tfrac{1}{2} \textup{ feet}\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 18\ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 18\ inches:x\ feet\rightarrow \frac{18\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{18\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=18\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=18\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{18}{12}\)

Solve.

\(\displaystyle x=1 \tfrac{1}{2} \ feet\)

The carpenter needs \(\displaystyle 1 \tfrac{1}{2} \ feet\) of material.

Example Question #73 : Ratios & Proportional Relationships

A carpenter is making a model house and he buys \(\displaystyle 8\textup{ feet}\) of crown moulding to use as accent pieces. He needs \(\displaystyle 9\textup{ inches}\) of the moulding for the house. How many feet of the material does he need to finish the model?

Possible Answers:

\(\displaystyle \frac {1}{4} \textup{ feet}\)

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

\(\displaystyle \frac {2}{3} \textup{ feet}\)

\(\displaystyle \frac {3}{4} \textup{ feet}\)

\(\displaystyle \frac {1}{2} \textup{ feet}\)

Correct answer:

\(\displaystyle \frac {3}{4} \textup{ feet}\)

Explanation:

We can solve this problem using ratios. There are \(\displaystyle 12\ inches\) in \(\displaystyle 1\ foot\). We can write this relationship as the following ratio:

\(\displaystyle 12\ inches:1\ foot\rightarrow \frac{12\ inches}{1\ foot}\)

We know that the carpenter needs \(\displaystyle 9 \ inches\) of material to finish the house. We can write this as a ratio using the variable \(\displaystyle x\) to substitute the amount of feet.

\(\displaystyle 9\ inches:x\ feet\rightarrow \frac{9\ inches}{x\ feet}\)

Now, we can solve for \(\displaystyle x\) by creating a proportion using our two ratios.

\(\displaystyle \frac{12\ inches}{1\ foot}=\frac{9\ inches}{x\ feet}\)

Cross multiply and solve for \(\displaystyle x\).

\(\displaystyle 12\ inches \times (x\ feet)=9\ inches \times (1\ foot)\)

Simplify.

\(\displaystyle 12x=9\)

Divide both sides by \(\displaystyle 12\).

\(\displaystyle \frac{12x}{12}=\frac{9}{12}\)

Solve.

\(\displaystyle x=\frac{9}{12} \ feet\)

Reduce.

\(\displaystyle x=\frac{3}{4} \ feet\)

The carpenter needs \(\displaystyle \frac {3}{4} \ feet\) of material.

Learning Tools by Varsity Tutors