Algebra 1 : Proportions

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #71 : Proportions

Solve the proportion:  \(\displaystyle \frac{2x}{9} = \frac{4}{3}\)

Possible Answers:

\(\displaystyle \frac{13}{6}\)

\(\displaystyle 6\)

\(\displaystyle \frac{81}{2}\)

\(\displaystyle \frac{1}{6}\)

\(\displaystyle \frac{13}{5}\)

Correct answer:

\(\displaystyle 6\)

Explanation:

To solve the proportion, cross multiply the fractions.

\(\displaystyle (2x)(3)=(9)(4)\)

Simplify both sides.

\(\displaystyle 6x=36\)

Divide by six on both sides.

\(\displaystyle \frac{6x}{6}=\frac{36}{6}\)

Simplify both sides.

The answer is:  \(\displaystyle x=6\)

Example Question #71 : Proportions

Solve the proportion:  \(\displaystyle \frac{6}{x} = \frac{1}{7}\)

Possible Answers:

\(\displaystyle 13\)

\(\displaystyle 1\)

\(\displaystyle 42\)

\(\displaystyle \frac{7}{6}\)

\(\displaystyle \frac{6}{7}\)

Correct answer:

\(\displaystyle 42\)

Explanation:

Cross multiply the fractions.

\(\displaystyle (6)(7)=(x)(1)\)

Simplify both sides.

\(\displaystyle x=42\)

The answer is:  \(\displaystyle 42\)

Example Question #73 : Proportions

Solve the proportion:  \(\displaystyle \frac{2x+3}{6} = \frac{4x-3}{5}\)

Possible Answers:

\(\displaystyle -\frac{14}{33}\)

\(\displaystyle \frac{14}{33}\)

\(\displaystyle \frac{33}{14}\)

\(\displaystyle -\frac{33}{14}\)

\(\displaystyle \frac{33}{8}\)

Correct answer:

\(\displaystyle \frac{33}{14}\)

Explanation:

Cross multiply the fractions.

\(\displaystyle (2x+3)(5)=(4x-3)(6)\)

Use the distributive property to simplify the equation.

\(\displaystyle 10x+15= 24x-18\)

In order to group the terms, subtract \(\displaystyle 10x\) on both sides, and add 18 on both sides.

\(\displaystyle 10x+15 -(10x)+[18]= 24x-18-(10x)+[18]\)

Simplify the equation.

\(\displaystyle 33 = 14x\)

Divide by 14 on both sides and simplify.

\(\displaystyle \frac{33}{14} = \frac{14x}{14}\)

\(\displaystyle x=\frac{33}{14}\)

The answer is:  \(\displaystyle \frac{33}{14}\)

Example Question #74 : Proportions

Solve the proportion:  \(\displaystyle \frac{3}{8x}= \frac{8}{3}\)

Possible Answers:

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

\(\displaystyle \frac{9}{64}\)

\(\displaystyle \frac{64}{9}\)

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

\(\displaystyle 1\)

Correct answer:

\(\displaystyle \frac{9}{64}\)

Explanation:

In order to solve for the unknown variable, cross multiply both fractions.

\(\displaystyle (3)(3)= (8)(8x)\)

Simplify both sides.

\(\displaystyle 9=64x\)

Divide by 64 on both sides.

\(\displaystyle x= \frac{9}{64}\)

The answer is:  \(\displaystyle \frac{9}{64}\)

Example Question #75 : Proportions

Solve the proportion:  \(\displaystyle \frac{2}{x} = \frac{3}{x+2}\)

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle \frac{4}{5}\)

\(\displaystyle 1\)

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

\(\displaystyle \frac{1}{3}\)

Correct answer:

\(\displaystyle 4\)

Explanation:

Cross multiply the two fractions.

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

Distribute the left side.

\(\displaystyle 2x+4=3x\)

Subtract \(\displaystyle 2x\) from both sides.

\(\displaystyle 2x+4-2x=3x-2x\)

Simplify both sides.

\(\displaystyle 4=x\)

The answer is:  \(\displaystyle 4\)

Example Question #76 : Proportions

Solve the proportion:  \(\displaystyle \frac{8}{7x} =\frac{3}{4}\)

Possible Answers:

\(\displaystyle \frac{7}{3}\)

\(\displaystyle \frac{6}{5}\)

\(\displaystyle \frac{28}{11}\)

\(\displaystyle \frac{3}{7}\)

\(\displaystyle \frac{32}{21}\)

Correct answer:

\(\displaystyle \frac{32}{21}\)

Explanation:

Cross multiply the two fractions.

\(\displaystyle 8(4)= (7x)(3)\)

Simplify both sides.

\(\displaystyle 32 = 21x\)

Divide by 21 on both sides to isolate the x-variable.

\(\displaystyle \frac{32}{21} =\frac{ 21x}{21}\)

Reduce the right side of the equation.  The left side of the equation is irreducible.

The answer is:  \(\displaystyle x=\frac{32}{21}\)

Example Question #77 : Proportions

Solve the proportion:   \(\displaystyle \frac{3}{4} = \frac{2(x+2)}{3}\)

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle \frac{1}{8}\)

\(\displaystyle 0\)

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

\(\displaystyle -\frac{7}{8}\)

Correct answer:

\(\displaystyle -\frac{7}{8}\)

Explanation:

Cross multiply the two fractions.

\(\displaystyle (3)(3)= 2(4)(x+2)\)

Simplify both sides of the equation.

\(\displaystyle 9=8x+16\)

Subtract 16 from both sides and simplify the equation.

\(\displaystyle 9-16=8x+16-16\)

\(\displaystyle -7=8x\)

Divide by eight on both sides.

\(\displaystyle \frac{-7}{8}=\frac{8x}{8}\)

The answer is:  \(\displaystyle x=-\frac{7}{8}\)

Example Question #78 : Proportions

Solve the proportion:  \(\displaystyle \frac{2}{x+1} = \frac{3}{x+2}\)

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle -\frac{2}{3}\)

\(\displaystyle -\frac{3}{2}\)

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

\(\displaystyle -1\)

Correct answer:

\(\displaystyle 1\)

Explanation:

To solve the proportion, cross multiply both sides of the equation.

\(\displaystyle 2(x+2)=3(x+1)\)

Distribute the terms to simplify.

\(\displaystyle 2x+4=3x+3\)

Subtract \(\displaystyle 2x\) from both sides.

\(\displaystyle 4=x+3\)

Subtract three from both sides.

\(\displaystyle x=1\)

The answer is:  \(\displaystyle 1\)

Example Question #79 : Proportions

Solve the proportion:  \(\displaystyle \frac{3x}{2x+1} = \frac{8}{3}\)

Possible Answers:

\(\displaystyle -\frac{10}{13}\)

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

\(\displaystyle -\frac{8}{7}\)

\(\displaystyle \textup{No solution.}\)

\(\displaystyle -\frac{1}{7}\)

Correct answer:

\(\displaystyle -\frac{8}{7}\)

Explanation:

Before we cross multiply, we have to make sure to note that there is an \(\displaystyle x\) existent in the denominator.  Recall that a denominator cannot be zero.

Set the denominator equal to zero and solve for \(\displaystyle x\).

\(\displaystyle 2x+1=0\)

\(\displaystyle 2x=-1\)

\(\displaystyle x=-\frac{1}{2}\)

The final answer cannot be \(\displaystyle x=-\frac{1}{2}\) after solving the proportion.

Cross multiply the fractions given.

\(\displaystyle 3(3x)=8(2x+1)\)

Simplify by distribution.

\(\displaystyle 9x=16x+8\)

Subtract \(\displaystyle 9x\) on both sides and simplify.

\(\displaystyle 9x-9x=16x+8-9x\)

\(\displaystyle 0=7x+8\)

Subtract \(\displaystyle 8\) on both sides.

\(\displaystyle -8=7x\)

Divide by \(\displaystyle 7\)on both sides.

\(\displaystyle \frac{-8}{7}=\frac{7x}{7}\)

The answer is:  \(\displaystyle x=-\frac{8}{7}\)

Example Question #80 : Proportions

Solve the proportion:  \(\displaystyle \frac{3x}{7} = \frac{1}{14}\)

Possible Answers:

\(\displaystyle \frac{1}{6}\)

\(\displaystyle -\frac{1}{6}\)

\(\displaystyle 6\)

\(\displaystyle -\frac{97}{3}\)

\(\displaystyle \frac{97}{3}\)

Correct answer:

\(\displaystyle \frac{1}{6}\)

Explanation:

Cross multiply both fractions.

\(\displaystyle (3x)(14) = 7(1)\)

Simplify both sides.

\(\displaystyle 42x=7\)

In order to isolate x, we will need to divide both sides by 42.

\(\displaystyle \frac{42x}{42}=\frac{7}{42}\)

Reduce both fractions on the left and right side.

The answer is:  \(\displaystyle x= \frac{1}{6}\)

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