SSAT Upper Level Math : Rational Numbers

Study concepts, example questions & explanations for SSAT Upper Level Math

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Example Questions

Example Question #4 : How To Find A Complex Fraction

Simplify:

\displaystyle \frac{3\frac{1}{2}-2\frac{1}{5}}{4\frac{3}{4}}

Possible Answers:

\displaystyle \frac{27}{100}

\displaystyle \frac{9}{23}

The correct answer is not given among the other responses.

\displaystyle \frac{5}{19}

\displaystyle \frac{7}{25}

Correct answer:

The correct answer is not given among the other responses.

Explanation:

\displaystyle \frac{3\frac{1}{2}-2\frac{1}{5}}{4\frac{3}{4}}

\displaystyle = \left ( \frac{7}{2}- \frac{11}{5} \right ) \div \frac{19}{4}

\displaystyle = \left ( \frac{35}{10}- \frac{22}{10} \right ) \times \frac{4}{19}

\displaystyle = \frac{13}{10} \times \frac{4}{19}

\displaystyle = \frac{13}{5} \times \frac{2}{19}

\displaystyle = \frac{26}{95}

This is not among the given responses.

Example Question #81 : Fractions

Simplify:

\displaystyle \frac{3\frac{1}{2}+2\frac{1}{5}}{4\frac{3}{4}}

Possible Answers:

\displaystyle 1\frac{3}{5}

\displaystyle 1\frac{1}{4}

\displaystyle 1\frac{1}{5}

\displaystyle 1\frac{1}{6}

\displaystyle 1\frac{2}{5}

Correct answer:

\displaystyle 1\frac{1}{5}

Explanation:

\displaystyle \frac{3\frac{1}{2}+2\frac{1}{5}}{4\frac{3}{4}}

\displaystyle = \left ( \frac{7}{2}+ \frac{11}{5} \right ) \div \frac{19}{4}

\displaystyle = \left ( \frac{35}{10}+ \frac{22}{10} \right ) \times \frac{4}{19}

\displaystyle = \frac{57}{10} \times \frac{4}{19}

\displaystyle = \frac{3}{5} \times \frac{2}{1}

\displaystyle = \frac{6}{5} = 1\frac{1}{5}

Example Question #4 : How To Find A Complex Fraction

Simplify, writing as a proper fraction.

Possible Answers:

\displaystyle \frac{5}{9}

\displaystyle \frac{2}{5}

\displaystyle \frac{5}{12}

\displaystyle \frac{3}{10}

\displaystyle \frac{7}{12}

Correct answer:

\displaystyle \frac{5}{12}

Explanation:

Remember that that fraction bar is just a division symbol. Rewrite as a division, rewrite those mixed fractions as improper fractions, then rewrite as as a multiplication by the reciprocal of the second fraction.

Example Question #1211 : Ssat Upper Level Quantitative (Math)

Simplify.

\displaystyle \frac{2}{x^2}-\frac{4}{x}

Possible Answers:

\displaystyle \frac{2}{x^2}

\displaystyle \frac{-2}{x^2-x}

\displaystyle \frac{4}{x}

\displaystyle \frac{x^2-x}{2}

\displaystyle \frac{2-4x}{x^2}

Correct answer:

\displaystyle \frac{2-4x}{x^2}

Explanation:

Find the least common denominator which is \displaystyle x^2.

Just multiply the right fraction top and bottom by \displaystyle x

\displaystyle \frac{2}{x^2}-\frac{4\cdot x}{x \cdot x}=\frac{2}{x^2}-\frac{4x}{x^2}

Finally, subtract. 

Answer should be, 

 \displaystyle \frac{2-4x}{x^2}.

Example Question #2 : How To Subtract Complex Fractions

Simplify.

\displaystyle \frac{x^2-5x+6}{x^2+2x-8}-\frac{x^2-5x-6}{x^2+x-12}

Possible Answers:

\displaystyle \frac{-1}{x+4}

\displaystyle \frac{2x-4}{x+4}

\displaystyle \frac{x-5}{x+4}

\displaystyle \frac{-5}{x+4}

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

Correct answer:

\displaystyle \frac{-1}{x+4}

Explanation:

Lets try to factor. Remember, we need to find two terms that are factors of the c term that add up to the b term. 

\displaystyle \frac{(x-2)(x-3)}{(x-2)(x+4)}-\frac{(x-3)(x-2)}{(x-3)(x+4)} 

Next cancel out the like terms.

\displaystyle \frac{x-3}{x+4}-\frac{x-2}{x+4} 

Now combine the numerator. Remember to distribute the negative sign.

This is the final answer:

 \displaystyle \frac{-1}{x+4}.

 

Example Question #3 : How To Subtract Complex Fractions

Simplify.

\displaystyle 1-\frac{3}{x-3}

Possible Answers:

\displaystyle \frac{3}{x-3}

\displaystyle \frac{x-6}{x-3}

\displaystyle \frac{x+6}{x-3}

\displaystyle 1

\displaystyle \frac{1}{x-3}

Correct answer:

\displaystyle \frac{x-6}{x-3}

Explanation:

Turn the \displaystyle 1 into a fraction that has a common denominator with the other fraction. To do this multiply \displaystyle 1 \cdot \frac{x-3}{x-3}.

This results in the following expression:

\displaystyle \frac{x-3}{x-3}-\frac{3}{x-3}

With the same denominator, just subtract and remember to distribute the negative sign.

The final answer is

 \displaystyle \frac{x-6}{x-3}.

Example Question #1 : How To Subtract Complex Fractions

Solve and simplify.

\displaystyle \frac{x^2-9}{x+3}-\frac{x^2-16}{x+4}

Possible Answers:

\displaystyle \frac{x^2+7}{x^2+7x+12}

\displaystyle \frac{2x}{x^2+7x+12}

\displaystyle \frac{1}{x^2+7x+12}

\displaystyle \frac{7}{x^2+7x+12}

\displaystyle 1

Correct answer:

\displaystyle 1

Explanation:

Lets try to reduce the fraction. When factoring a difference of squares, the form is \displaystyle (x-a)(x+a). When you foil, the middle terms cancel out.

So when doing that, we have:

\displaystyle \frac{(x-3)(x+3)}{(x+3)}-\frac{(x-4)(x+4)}{(x+4)}.

Cancel out like terms and we get this:

\displaystyle (x-3)-(x-4).

Distribute the negative sign and we should get \displaystyle 1.

Example Question #82 : Rational Numbers

Solve for \displaystyle x.

\displaystyle \frac{1}{\sqrt{x}}-\frac{1}{2\sqrt{x}}=2

Possible Answers:

\displaystyle 4

\displaystyle {}\frac{1}{4}

\displaystyle {}\frac{1}{2}

\displaystyle 16

\displaystyle \frac{1}{16}

Correct answer:

\displaystyle \frac{1}{16}

Explanation:

First find the least common denominator. That will be  \displaystyle 2\sqrt{x} .

Multiply top and bottom of the left fraction by \displaystyle 2 .

\displaystyle \frac{1}{\sqrt{x}}\cdot \frac{2}{2}=\frac{2}{2\sqrt{x}}

Then subtract the numerator and then cross-multiply to get this: 

\displaystyle \frac{2}{2\sqrt{2}}-\frac{1}{2\sqrt{2}}=2\rightarrow 2-1=2(2\sqrt{x}) \rightarrow 1=4\sqrt{x}

Then combine like terms. To get rid of the square root,

\displaystyle \frac{1}{4}=\sqrt{x} square both sides to get \displaystyle \left(\frac{1}{4}\right)^2=\frac{1}{16} as the final answer.

Example Question #1 : How To Subtract Complex Fractions

Solve for \displaystyle x.

\displaystyle \frac{5}{x-2}-\frac{2}{x+2}=1

Possible Answers:

\displaystyle 1

\displaystyle -6

\displaystyle 2

\displaystyle 3

Both \displaystyle 6 and \displaystyle -3.

Correct answer:

Both \displaystyle 6 and \displaystyle -3.

Explanation:

Find the least common denominator which is \displaystyle x^2-4. Then multiply the left fraction numerator by \displaystyle x+2 and multiply the right numerator by \displaystyle x-2 inorder for each fraction to share the common denominator.

\displaystyle \frac{5(x+2)}{x^2-4}-\frac{2(x-2)}{x^2-4}=1 

Distribute and be careful of the negative sign.

\displaystyle \frac{5x+10-2x+4}{x^2-4}=1 

Cross-multiply and create the quadratic equation.

\displaystyle x^2-3x-18=0 

Lets factor. Remember, we need to find two terms that are factors of the c term that add up to the b term. 

\displaystyle (x-6)(x+3)=0

\displaystyle x=6\displaystyle x=-3

If you check these answers back into the question, none of the fractions are undefined so these are the final answers. 

Example Question #7 : How To Subtract Complex Fractions

Solve for \displaystyle x.

\displaystyle \frac{2}{x-1}-\frac{2}{x+1}=\left | 2\right |

Possible Answers:

\displaystyle -3

\displaystyle -\sqrt{3}

\displaystyle \sqrt{3}

\displaystyle 3

\displaystyle \pm\sqrt{3}

Correct answer:

\displaystyle \pm\sqrt{3}

Explanation:

Find the least common denominator which is \displaystyle x^2-1. Then multiply the left fraction numerator by \displaystyle x+1 and multiply the right numerator by \displaystyle x-1 in order to make each fraction share the common denominator.

\displaystyle \frac{2(x+1)}{x^2-1}-\frac{2(x-1)}{x^2-1}=\left | 2\right | 

Distribute and be careful of the negative sign.

\displaystyle \frac{2x+2-2x+2}{x^2-1}=\left | 2\right | 

Simplify the numerator and cross multiply. Because there is an absolute value bar, we need to split this expression into two different equations.

Equation one:

\displaystyle 2(x^2-1)=4

\displaystyle 2x^2-2=4

\displaystyle 2x^2=6

\displaystyle x^2=3

\displaystyle x=\pm \sqrt{3} By inspection, these values pass and don't violate the fractions being undefined.

Equation two:

\displaystyle -2(x^2-1)=4

\displaystyle -2x^2+2=4

\displaystyle -2x^2=2

\displaystyle x^2=-1

\displaystyle x=i This answer is imaginary and not in the choices leaving \displaystyle \pm \sqrt{3} as the answers.

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