ISEE Middle Level Math : How to multiply fractions

Study concepts, example questions & explanations for ISEE Middle Level Math

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Example Questions

Example Question #222 : Fractions

Multiply the following:

\(\displaystyle \frac{6}{7} \cdot\frac{1}{2}\)

Possible Answers:

\(\displaystyle \frac{19}{14}\)

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

\(\displaystyle \frac{7}{9}\)

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

\(\displaystyle \frac{6}{12}\)

Correct answer:

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

Explanation:

To multiply fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator.

\(\displaystyle \frac{6}{7} \cdot\frac{1}{2}\)

\(\displaystyle \frac{6 \cdot 1}{7 \cdot 2}\)

\(\displaystyle \frac{6}{14}\)

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

Example Question #371 : Numbers And Operations

Multiply the following:

\(\displaystyle \frac{1}{2} \cdot \frac{1}{2}\)

Possible Answers:

\(\displaystyle \frac{1}{2}\)

\(\displaystyle 2\)

\(\displaystyle 1\)

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

\(\displaystyle \frac{1}{4}\)

Correct answer:

\(\displaystyle \frac{1}{4}\)

Explanation:

To multiply fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator.

So,

\(\displaystyle \frac{1}{2} \cdot \frac{1}{2}\)

\(\displaystyle \frac{1 \cdot 1}{2 \cdot 2}\)

\(\displaystyle \frac{1}{4}\)

Example Question #371 : Numbers And Operations

Multiply the following:

\(\displaystyle \frac{1}{4} \cdot \frac{1}{4}\)

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle \frac{1}{4}\)

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

\(\displaystyle \frac{1}{16}\)

\(\displaystyle \frac{1}{2}\)

Correct answer:

\(\displaystyle \frac{1}{16}\)

Explanation:

To multiply fractions, we will multiply the numerators together, then we will multiply the denominators together. Note that we do NOT need to find a common denominator.

So,

\(\displaystyle \frac{1}{4} \cdot \frac{1}{4}\)

\(\displaystyle \frac{1 \cdot 1}{4 \cdot 4}\)

\(\displaystyle \frac{1}{16}\)

Example Question #223 : Fractions

Multiply the following:

\(\displaystyle \frac{2}{5} \cdot \frac{1}{5}\)

Possible Answers:

\(\displaystyle \frac{3}{10}\)

\(\displaystyle \frac{3}{25}\)

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

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

\(\displaystyle \frac{2}{5}\)

Correct answer:

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

Explanation:

To multiply fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator. 

So,

\(\displaystyle \frac{2}{5} \cdot \frac{1}{5}\)

\(\displaystyle \frac{2 \cdot 1}{5 \cdot 5}\)

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

Example Question #231 : Fractions

Multiply the following:

\(\displaystyle \frac{1}{3} \cdot \frac{2}{3}\)

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle \frac{2}{9}\)

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

\(\displaystyle \frac{3}{6}\)

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

Correct answer:

\(\displaystyle \frac{2}{9}\)

Explanation:

To multiply fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator.  

So, given the problem

\(\displaystyle \frac{1}{3} \cdot \frac{2}{3}\)

we will multiply straight across.  We get

\(\displaystyle \frac{1 \cdot 2}{3 \cdot 3}\)

\(\displaystyle \frac{2}{9}\)

Example Question #41 : How To Multiply Fractions

Multiply the following:

\(\displaystyle \frac{2}{5} \cdot \frac{1}{5}\)

Possible Answers:

\(\displaystyle \frac{3}{25}\)

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

\(\displaystyle \frac{2}{5}\)

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

\(\displaystyle \frac{3}{10}\)

Correct answer:

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

Explanation:

When multiplying fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT have to find a common denominator.  

So, 

\(\displaystyle \frac{2}{5} \cdot \frac{1}{5}\)

\(\displaystyle \frac{2 \cdot 1}{5 \cdot 5}\)

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

Example Question #41 : How To Multiply Fractions

Multiply the following:

\(\displaystyle \frac{a}{b} \cdot \frac{c}{d}\)

Possible Answers:

\(\displaystyle \frac{ab}{cd}\)

\(\displaystyle abcd\)

\(\displaystyle ab \cdot cd\)

\(\displaystyle \frac{ad}{bc}\)

\(\displaystyle \frac{ac}{bd}\)

Correct answer:

\(\displaystyle \frac{ac}{bd}\)

Explanation:

When multiplying fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator.  

So, given the problem

\(\displaystyle \frac{a}{b} \cdot \frac{c}{d}\)

we will multiply straight across.  We get

\(\displaystyle \frac{a \cdot c}{b \cdot d}\)

\(\displaystyle \frac{ac}{bd}\)

 

Note that when variables are being multiplied together, we can write them right next to each other (side by side).  

In other words, 

\(\displaystyle ac\) 

is the same as 

\(\displaystyle a \cdot c\) 

or 

\(\displaystyle a\) times \(\displaystyle c\)

Example Question #381 : Numbers And Operations

Multiply the following: 

\(\displaystyle \frac{3}{4} \cdot \frac{1}{2}\)

Possible Answers:

\(\displaystyle \frac{6}{16}\)

\(\displaystyle \frac{4}{6}\)

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

\(\displaystyle \frac{6}{4}\)

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

Correct answer:

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

Explanation:

When multiplying fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator. 

So, given the problem

\(\displaystyle \frac{3}{4} \cdot \frac{1}{2}\)

we will multiply straight across.  We get

\(\displaystyle \frac{3 \cdot 1}{4 \cdot 2}\)

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

Example Question #231 : Fractions

Multiply the following:

\(\displaystyle \frac{2}{5} \cdot \frac{7}{8}\)

Possible Answers:

\(\displaystyle \frac{9}{13}\)

\(\displaystyle \frac{7}{20}\)

\(\displaystyle \frac{16}{35}\)

\(\displaystyle \frac{51}{80}\)

\(\displaystyle \frac{51}{40}\)

Correct answer:

\(\displaystyle \frac{7}{20}\)

Explanation:

To multiply fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator. 

So, in the problem

\(\displaystyle \frac{2}{5} \cdot \frac{7}{8}\)

we will multiply straight across.  Before we multiply, we will simplify to make things easier.  

The 2 and the 8 can both be divided by 2.  So, we get

\(\displaystyle \frac{1}{5} \cdot \frac{7}{4}\)

Now, we can multiply straight across.  We get

\(\displaystyle \frac{1 \cdot 7}{5 \cdot 4}\)

\(\displaystyle \frac{7}{20}\)

Example Question #236 : Fractions

Multiply the following:

\(\displaystyle \frac{4}{5} \cdot 25\)

Possible Answers:

\(\displaystyle 20\)

\(\displaystyle 30\)

\(\displaystyle 15\)

\(\displaystyle 25\)

\(\displaystyle 40\)

Correct answer:

\(\displaystyle 20\)

Explanation:

To multiply fractions, we will multiply the numerators together, then we will multiply the denominators together.  Note that we do NOT need to find a common denominator. 

So, in the problem 

\(\displaystyle \frac{4}{5} \cdot 25\)

we first need to write 25 as a fraction.  We know that whole numbers can be written as fractions over 1.  So, we get

\(\displaystyle \frac{4}{5} \cdot \frac{25}{1}\)

Now, we can simplify before we multiply to make things easier.  The 5 and the 25 can both be divided by 5.  So, we get

\(\displaystyle \frac{4}{1} \cdot \frac{5}{1}\)

Now, we will multiply straight across.  We get

\(\displaystyle \frac{4 \cdot 5}{1 \cdot 1}\)

\(\displaystyle \frac{20}{1}\)

\(\displaystyle 20\)

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