Pre-Algebra : One-Step Equations with Fractions

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #1 : One Step Equations With Fractions

Solve for \displaystyle x:

\displaystyle \frac{x}{\frac{2}{3}}=6

Possible Answers:

\displaystyle 3

\displaystyle 4

\displaystyle 8

\displaystyle 9

Correct answer:

\displaystyle 4

Explanation:

Isolate the variable to one side.

Multiply each side by \displaystyle \frac{2}{3}:

\displaystyle \frac{x}{\frac{2}{3}}=6

\displaystyle \frac{x\frac{2}{3}}{\frac{2}{3}}=\frac{6}{1}*\frac{2}{3}

Simplify and reduce:

\displaystyle x=4

Example Question #2 : One Step Equations With Fractions

Solve for \displaystyle x:

\displaystyle \frac{2}{5}x=8

Possible Answers:

\displaystyle 8\frac{2}{5}

\displaystyle 20

\displaystyle 16

\displaystyle 40

\displaystyle 3\frac{1}{5}

Correct answer:

\displaystyle 20

Explanation:

Step 1: Multiply both sides of the equation by the fraction's reciprocal to get \displaystyle x alone on one side:

\displaystyle \frac{5}{2}*\frac{2}{5}x=8*\frac{5}{2}

\displaystyle 1x=8*\frac{5}{2}

\displaystyle x=8*\frac{5}{2}

Step 2: Multiply:

\displaystyle x=8*\frac{5}{2}=\frac{40}{2}=20

 

Example Question #3 : One Step Equations With Fractions

Solve for \displaystyle x:

\displaystyle \frac{x}{\frac{4}{5}} = 2

Possible Answers:

\displaystyle \frac{8}{5}

\displaystyle \frac{10}{4}

\displaystyle \frac{5}{8}

\displaystyle \frac{8}{10}

\displaystyle \frac{4}{10}

Correct answer:

\displaystyle \frac{8}{5}

Explanation:

The goal is to isolate the variable on one side.

\displaystyle \frac{x}{\frac{4}{5}} = 2

The opposite operation of division is multiplication, therefore , multiply each side by \displaystyle \frac{4}{5}:

\displaystyle \frac{\frac{4}{5}x}{\frac{4}{5}} = \frac{4}{5}\times 2

The left hand side can be reduced by recalling that anything divided by itself is equal to 1:

\displaystyle 1\times x = \frac{4}{5} \times 2

The identity law of multiplication takes effect and we get the solution as:

\displaystyle x = \frac{8}{5}

Example Question #3 : One Step Equations With Fractions

Solve for \displaystyle x:

\displaystyle \frac{6}{7} x = 3

Possible Answers:

\displaystyle \frac{18}{7}

\displaystyle \frac{7}{2}

\displaystyle \frac{18}{21}

\displaystyle \frac{21}{18}

\displaystyle \frac{18}{6}

Correct answer:

\displaystyle \frac{7}{2}

Explanation:

The goal is to isolate the variable on one side.

\displaystyle \frac{6}{7} x = 3

The opposite operation of multiplication is division, therefore, we can either divide each side by \displaystyle \frac{6}{7} or multiply each side by its reciprocal \displaystyle \frac{7}{6}:

\displaystyle \frac{7}{6}\times \frac{6}{7}x = \frac{7}{6}\times 3

The left hand side can be reduced by recalling that anything multiplying a fraction by its reciprocal is equal to 1:

\displaystyle 1\times x = \frac{7}{6} \times 3

The identity law of multiplication takes effect and we get the solution as:

\displaystyle x = \frac{21}{6}

However, this solution can be reduced by dividing both the numerator and denominator by 3:

\displaystyle x = \frac{7}{2}

Example Question #4 : One Step Equations With Fractions

Solve for \displaystyle x:

\displaystyle x + \frac{7}{3} = \frac{1}{6}

Possible Answers:

\displaystyle \frac{8}{3}

\displaystyle \frac{13}{6}

\displaystyle -\frac{6}{13}

\displaystyle -\frac{13}{6}

\displaystyle \frac{8}{6}

Correct answer:

\displaystyle -\frac{13}{6}

Explanation:

The goal is to isolate the variable on one side.

\displaystyle x + \frac{7}{3} = \frac{1}{6}

The opposite operation of addition is subtraction so subtract \displaystyle \frac{7}{3} from each side:

\displaystyle x + \frac{7}{3} - \frac{7}{3} = \frac{1}{6} - \frac{7}{3}

In order to complete the subtraction on the right hand side, we must first determine the common denominator, or common multiples of 3 and 6. The least common multiple of 3 and 6 is 6 itself.

\displaystyle x = \frac{1}{6} - \frac{14}{6}

Simplifying, we get the final solution:

\displaystyle x = -\frac{13}{6}

Example Question #5 : One Step Equations With Fractions

Solve for \displaystyle x:

\displaystyle x - \frac{5}{6} = \frac{5}{12}

Possible Answers:

\displaystyle \frac{5}{4}

\displaystyle \frac{13}{12}

\displaystyle \frac{10}{12}

\displaystyle \frac{7}{12}

\displaystyle -\frac{5}{4}

Correct answer:

\displaystyle \frac{5}{4}

Explanation:

The goal is to isolate the variable on one side.

\displaystyle x - \frac{5}{6} = \frac{5}{12}

The opposite operation of subtraction is addition so add \displaystyle \frac{5}{6} to each side:

\displaystyle x - \frac{5}{6} + \frac{5}{6} = \frac{5}{12} + \frac{5}{6}

In order to complete the addition on the right hand side, we must first determine the common denominator, or common multiples of 6 and 12. The least common multiple of 6 and 12 is 12 itself.

\displaystyle x = \frac{5}{12} + \frac{10}{12}

Simplifying, we obtain the solution:

\displaystyle x = \frac{15}{12}

Reducing the fraction to its simplest terms we get the final solution:

\displaystyle x = \frac{5}{4}

Example Question #7 : One Step Equations With Fractions

Solve for y

\displaystyle 6y=15

Possible Answers:

\displaystyle y=\frac{5}{2}

\displaystyle y=90

\displaystyle y=6

\displaystyle y=\frac{6}{15}

\displaystyle y=\frac{5}{6}

Correct answer:

\displaystyle y=\frac{5}{2}

Explanation:

To get y by itself, you must divide by 6 on both sides

\displaystyle \frac{6y}{6}=\frac{15}{6}

which simplifies to

\displaystyle y=\frac{15}{6}=\frac{5}{2}

Example Question #5 : One Step Equations With Fractions

Solve for x

\displaystyle \frac{x}{5}=\frac{1}{3}

Possible Answers:

\displaystyle x=\frac{3}{5}

\displaystyle x=3

\displaystyle x=5

\displaystyle x=\frac{1}{5}

\displaystyle x=\frac{5}{3}

Correct answer:

\displaystyle x=\frac{5}{3}

Explanation:

To get x by itself, you must multiply both sides of the equation by 5

\displaystyle \frac{x}{5}\times5=\frac{1}{3}\times5

which simplifies to

\displaystyle x=\frac{5}{3}

Example Question #6 : One Step Equations With Fractions

Solve the equation below for x:

\displaystyle \small \small \frac{1}{5}x=5

Possible Answers:

\displaystyle \small 5

\displaystyle \small \small 25

\displaystyle \small 50

\displaystyle \small 45

\displaystyle \small 125

Correct answer:

\displaystyle \small \small 25

Explanation:

For this equation, isolate the variable \displaystyle \small x by preforming equivalent operations on both sides of the equation.

To isolate a variable multiplied by a fraction, any fraction multiplied by it's reciprocal equals one. 

\displaystyle \small \left(\frac{5}{1}\right)\small \frac{1}{5}x=5\left(\frac{5}{1}\right)

Because \displaystyle \small \frac{5}{5} = 1, we isolate \displaystyle \small x, and the equation becomes \displaystyle \small x=5\cdot \left(\frac{5}{1}\right)

multiplying the values on the right side gives us

\displaystyle \small x=\frac{25}{1}= 25

Example Question #7 : One Step Equations With Fractions

Solve for n:

\displaystyle \frac{3}{4}n=9

Possible Answers:

\displaystyle n=\frac{33}{4}

\displaystyle n=12

\displaystyle n=6

\displaystyle n=\frac{27}{4}

Correct answer:

\displaystyle n=12

Explanation:

\displaystyle \frac{3}{4}n=9

\displaystyle \frac{4}{3}\left(\frac{3}{4}\cdot n\right)=\left(\frac{4}{3}\right)\left(9 \right )

\displaystyle n=\frac{36}{3}=12

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