PSAT Math : Complex Fractions

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #1 : Complex Fractions

Simplify:

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

Possible Answers:

\(\displaystyle \frac{x}{x+2}\)

\(\displaystyle \frac{ x^{2}-2 }{ x^{2}+2}\)

\(\displaystyle \frac{ x^{2}+2x}{ x^{2}+2}\)

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

\(\displaystyle \frac{ x^{2}-2x}{ x^{2}+2}\)

Correct answer:

\(\displaystyle \frac{ x^{2}-2x}{ x^{2}+2}\)

Explanation:

Simplify the numerator and the denominator, then divide, as follows:

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

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

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

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

\(\displaystyle = \frac{ x-2}{x} \div \frac{x^{2}+2}{x^{2}}\)

\(\displaystyle = \frac{ x-2}{x} \cdot \frac{x^{2}}{x^{2}+2}\)

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

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

Example Question #82 : Fractions

Evaluate:

\(\displaystyle \frac{3+\frac{1}{4}}{3-\frac{1}{4}}\)

Possible Answers:

\(\displaystyle \frac{132}{16}\)

\(\displaystyle \frac{11}{13}\)

\(\displaystyle 2\)

\(\displaystyle \frac{13}{11}\)

\(\displaystyle \frac{16}{132}\)

Correct answer:

\(\displaystyle \frac{13}{11}\)

Explanation:

Simplify the numerator and the denominator, then divide, as follows:

\(\displaystyle \frac{3+\frac{1}{4}}{3-\frac{1}{4}}\)

\(\displaystyle =\frac{ \frac{12}{4}+\frac{1}{4}}{\frac{12}{4}-\frac{1}{4}}\)

\(\displaystyle =\frac{ \frac{13}{4}}{\frac{11}{4} }\)

\(\displaystyle = \frac{13}{4}\div \frac{11}{4}\)

\(\displaystyle = \frac{13}{4}\cdot \frac{4}{11}\)

\(\displaystyle = \frac{13}{1}\cdot \frac{1}{11}\)

\(\displaystyle = \frac{13}{11}\)

 

Example Question #1 : Complex Fractions

Solve:

\(\displaystyle 76-\frac{75}{6}=\)

Possible Answers:

\(\displaystyle \frac{127}{2}\)

\(\displaystyle 75\)

\(\displaystyle 74\)

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

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

Correct answer:

\(\displaystyle \frac{127}{2}\)

Explanation:

First reduce the fraction. We can divide both the numerator and the denominator by 3.

\(\displaystyle \frac{75\div 3}{6\div 3}=\frac{25}{2}\)

 

Now our expression looks like this:

\(\displaystyle 76-\frac{25}{2}\)

When you add or subtract fractions, you need to have the same denominator. The lowest common deonminator here is 2. So we need to multiply and solve:

\(\displaystyle \left ( \frac{2}{2}\right)\cdot76-\frac{25}{2}=\frac{152}{2}-\frac{25}{2}=\frac{127}{2}\)

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