High School Math : Pre-Algebra

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #23 : How To Solve One Step Equations With Fractions In Pre Algebra

Solve for \displaystyle x if \displaystyle x-\frac{7}{5}=\frac{5}{8}.

Possible Answers:

\displaystyle x=\frac{7}{8}

\displaystyle x=\frac{38}{9}

\displaystyle x=\frac{81}{40}

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

Correct answer:

\displaystyle x=\frac{81}{40}

Explanation:

To solve for  we must get all of the constants on the other side of the equation as .

To do this in a problem where  is being subtracted by a number, we must add the number to both sides of the equation.

In this case the number is \displaystyle \frac{7}{5} so we add \displaystyle \frac{7}{5} to each side of the equation: \displaystyle x-\frac{7}{5}+\frac{7}{5}=\frac{5}{8}+\frac{7}{5}

To add fractions we must first ensure that we have the same denominator.

To do this we must find the least common multiple of the denominators.

In this case the LCM is \displaystyle 40.

We then multiply \displaystyle \frac{5}{8}*\frac{5}{5} and \displaystyle \frac{7}{5}*\frac{8}{8} to get the same denominator for both fractions.

To multiply a fraction, multiply the top number of the first fraction by the top number of the second fraction and the bottom number of the first fraction by the bottom number of the second fraction.

 \displaystyle x=\frac{25}{40}+\frac{56}{40}

We then add the numerators together and place the result over the new denominator.

 \displaystyle x=\frac{81}{40}

 

Example Question #24 : How To Solve One Step Equations With Fractions In Pre Algebra

\displaystyle \frac{2}{7}x=18

Solve for \displaystyle x.

Possible Answers:

\displaystyle 16

\displaystyle 63

\displaystyle 5.14

\displaystyle 126

\displaystyle 9

Correct answer:

\displaystyle 63

Explanation:

Our goal here is to isolate \displaystyle x. That means we want just \displaystyle x on the left side.

For our problem, \displaystyle \frac{2}{7}x=18, we need to get rid of the fraction. Dividing by a fraction is the same as multiplying by the reciprocal.

\displaystyle \frac{2}{7}x=18

\displaystyle \frac{7}{2}*\frac{2}{7}x=18*\frac{7}{2}

\displaystyle \frac{14}{14}x=\frac{18*7}{2}

\displaystyle x=\frac{126}{2}

\displaystyle x=63

Example Question #29 : How To Solve One Step Equations With Fractions In Pre Algebra

\displaystyle 32=\frac{1}2{}x

Solve for \displaystyle x.

Possible Answers:

\displaystyle 66

\displaystyle 32

\displaystyle 34

\displaystyle 16

\displaystyle 64

Correct answer:

\displaystyle 64

Explanation:

When solving for \displaystyle x, we want to isolate it. That means we want only \displaystyle x on the right side of the equation.

For our given equation, \displaystyle 32=\frac{1}2{}x, we need to divide both sides by \displaystyle \frac{1}{2}.

Dividing by a fraction is the same as multiplying by the reciprocal so this will look like:

\displaystyle \frac{2}{1}*32=\frac{1}2{}x*\frac{2}{1}

\displaystyle \frac{2}{1}*\frac{32}{1}=\frac{1}2{}x*\frac{2}{1}

\displaystyle \frac{2*32}{1}=\frac{1*2}{2*1}x

\displaystyle \frac{64}{1}=\frac{2}{2}x

\displaystyle 64=x

Example Question #21 : How To Solve One Step Equations With Fractions In Pre Algebra

\displaystyle x=4*\frac{1}{2}

Solve for \displaystyle x.

Possible Answers:

\displaystyle 2

\displaystyle 4.2

\displaystyle 6

\displaystyle 4\tfrac{1}{2}

\displaystyle 8

Correct answer:

\displaystyle 2

Explanation:

\displaystyle x=4*\frac{1}{2}

\displaystyle x=\frac{4}{1}*\frac{1}{2}

\displaystyle x=\frac{4*1}{1*2}

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

\displaystyle x=2

Example Question #31 : How To Solve One Step Equations With Fractions In Pre Algebra

\displaystyle x=20*\frac{3}{2}

Solve for \displaystyle x.

Possible Answers:

\displaystyle 60

\displaystyle 30

\displaystyle 10

\displaystyle 13\tfrac{2}{3}

\displaystyle 13

Correct answer:

\displaystyle 30

Explanation:

\displaystyle x=20*\frac{3}{2}

\displaystyle x=\frac{20}{1}*\frac{3}{2}

\displaystyle x=\frac{20*3}{1*2}

\displaystyle x=\frac{60}{2}

\displaystyle x=30

Example Question #231 : Pre Algebra

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

What is \displaystyle x?

Possible Answers:

\displaystyle 5\tfrac{1}{5}

\displaystyle 25

\displaystyle 5

\displaystyle 1

\displaystyle 10

Correct answer:

\displaystyle 1

Explanation:

For this problem, multiply across on the right side:

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

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

Example Question #232 : Pre Algebra

\displaystyle x=12*\frac{1}{3}

What is \displaystyle x?

Possible Answers:

\displaystyle 12

\displaystyle 9

\displaystyle 3

\displaystyle 4

\displaystyle 15

Correct answer:

\displaystyle 4

Explanation:

To solve this problem, multiply across on the right side:

\displaystyle x=12*\frac{1}{3}=\frac{12}{1}*\frac{1}{3}=\frac{12}{3}=4

Example Question #34 : How To Solve One Step Equations With Fractions In Pre Algebra

\displaystyle \frac{2}{3}x=8.

Solve for \displaystyle x.

Possible Answers:

\displaystyle 32

\displaystyle 24

\displaystyle \frac{16}{3}

\displaystyle 6

\displaystyle 12

Correct answer:

\displaystyle 12

Explanation:

To divide both sides by a fraction, we multiply both sides by the reciprocal. 

\displaystyle \frac{3}{2}*\frac{2}{3}x=8*\frac{3}{2}

\displaystyle \frac{3*2}{2*3}x=\frac{8*3}{2}

\displaystyle \frac{6}{6}x=\frac{24}{2}

\displaystyle x=\frac{24}{2}

\displaystyle x=12

Example Question #1 : How To Solve One Step Equations With Decimals In Pre Algebra

Solve for  if  \displaystyle x+.12=.15

Possible Answers:

\displaystyle x=.03

\displaystyle x=.27

\displaystyle x=.15

\displaystyle x=.05

Correct answer:

\displaystyle x=.03

Explanation:

To solve for  we must get all of the numbers on the other side of the equation as .

To do this in a problem where a number is being added to , we must subtract the number from both sides of the equation.

In this case the number is \displaystyle .12 so we subtract \displaystyle .12 from each side of the equation to make it look like this \displaystyle x+.12-.12=.15-.12

The numbers on the left side cancel to leave  by itself.

To do the necessary subtraction we need to know how to subtract decimals from each other.

To subtract decimals you place the first decimal over the top of the other aligned by the decimal point. 

Then go through each place and subtract the top number by the bottom number.

Subtract the numbers in each place like you would any number \displaystyle 5-2=3 and \displaystyle 1-1=0

Combine the numbers and keep the decimal in the same place to get \displaystyle .15-.12=.03

The answer is \displaystyle x=.03

Example Question #1 : How To Solve One Step Equations With Decimals In Pre Algebra

Solve for \displaystyle x if \displaystyle .03x=.09 

Possible Answers:

\displaystyle .9

\displaystyle .3

\displaystyle 3

\displaystyle .03

Correct answer:

\displaystyle 3

Explanation:

To solve for \displaystyle x we must get all of the numbers on the other side of the equation of \displaystyle x.

To do this in a problem where \displaystyle x is being multiplied by a number, we must divide both sides of the equation by the number.

In this case the number is \displaystyle .03 so we divide each side of the equation by \displaystyle .03 to make it look like this \displaystyle \frac{.03x}{.03}=\frac{.09}{.03}

Then we must divide the decimals by each other to find the answer.

To divide decimals we line the decimals up like this \displaystyle \frac{.09}{.03}.

Then ignoring all of the decimal places we divide the top number by the bottom number to get \displaystyle \frac{9}{3}=3

Then we must apply the decimals.

However many decimal places there are in the denominator will be subtracted from the number of decimal places in the numerator to get the final number of decimal places in our answer.

If the number is positive we move the decimal that number of places to the left of our number.

If the number is negative we move the decimal that number of places to the right of our number.

In this case it would be \displaystyle 2-2=0 so we don't have any decimal places and the answer is  \displaystyle 3.

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