SAT Math : Arithmetic

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #611 : Arithmetic

Evaluate the following:

\(\displaystyle \left ( \frac{5}{6}\times \frac{12}{13} \right )^{2}\div \frac{3}{4}\)

Possible Answers:

\frac{400}{507}\(\displaystyle \frac{400}{507}\)

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

\frac{507}{400}\(\displaystyle \frac{507}{400}\)

None of the available answers

\frac{25}{507}\(\displaystyle \frac{25}{507}\)

Correct answer:

\frac{400}{507}\(\displaystyle \frac{400}{507}\)

Explanation:

\(\displaystyle \left ( \frac{5}{6}\times \frac{12}{13} \right )^{2}\div \frac{3}{4}\)

First we will evaluate the terms in the parentheses:

\(\displaystyle \left ( \frac{5}{6}\times \frac{2\times 6}{13} \right )^{2}\div \frac{3}{4}\)

\(\displaystyle \left ( \frac{5}{1}\times \frac{2}{13} \right )^{2}\div \frac{3}{4}\)

\(\displaystyle \left ( \frac{10}{13} \right )^{2}\div \frac{3}{4}\)

Next, we will square the first fraction:

\(\displaystyle \left ( \frac{10^{2}}{13^{2}} \right )\div \frac{3}{4}\)

\frac{100}{169}\div \frac{3}{4}\(\displaystyle \frac{100}{169}\div \frac{3}{4}\)

We can evaluate the division as such:

\frac{100}{169}\times\frac{4}{3}=\frac{400}{507}\(\displaystyle \frac{100}{169}\times\frac{4}{3}=\frac{400}{507}\)

Example Question #5 : How To Divide Fractions

Evaluate the expression:

\(\displaystyle \frac{3}{9}\div \frac{4}{15}\)

Possible Answers:

\(\displaystyle \frac{4}{45}\)

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

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

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

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

Correct answer:

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

Explanation:

When dividing fractions, you invert the second term and multiply the numbers. 

\(\displaystyle \frac{3}{9}\times\frac{15}{4}\) 

You can reduce the numbers that are diagonal from each other to make the numbers smaller and easier to multiply. 

\(\displaystyle \frac{3}{3}\times\frac{5}{4}=\frac{5}{4}=1\frac{1}{4}\)

Example Question #11 : Operations With Fractions

Simplify\(\displaystyle \frac{\frac{13x}{5y}}{\frac{3x}{8y}}\)

Possible Answers:

\(\displaystyle \frac{16}{13}\)

\(\displaystyle \frac{104}{15}\)

Fractions with variables cannot be divided

\(\displaystyle \frac{18}{8}\)

\(\displaystyle \frac{39}{40}\)

Correct answer:

\(\displaystyle \frac{104}{15}\)

Explanation:

When you dividing fractions, multiply by the reciprocal of the denominator.

\(\displaystyle \frac{\frac{13x}{5y}}{\frac{3x}{8y}}=\frac{13x}{5y}*\frac{8y}{3x}=\frac{13*x*8*y}{5*y*3*x}=\frac{13*8}{5*3}=\frac{104}{15}\)

Example Question #1 : How To Subtract Fractions

Which fraction has a value greater than that of X?

\(\displaystyle x = \frac{4}{3}-\frac{7}{12}\)

Possible Answers:

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

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

\(\displaystyle \frac{7}{8}\)

\(\displaystyle \frac{3}{4}\)

\(\displaystyle \frac{5}{7}\)

Correct answer:

\(\displaystyle \frac{7}{8}\)

Explanation:

First, start by putting changing the fractions in the equation so that they have the same denominator.

\(\displaystyle x=\frac{4}{3}-\frac{7}{12}\)

\(\displaystyle x=\frac{16}{12}-\frac{7}{12}\)

Then, you can easily subtract the numerators. The denominator stays the same at this point:

\(\displaystyle x=\frac{9}{12}\)

At this point, you can reduce the fraction by dividing the numerator and the denominator by \(\displaystyle 3\):

\(\displaystyle x=\frac{3}{4}\)

Then, to easily compare the fraction to the answer choices, you can change the fraction to a decimal:

\(\displaystyle \frac{3}{4}=0.75\)

By changing the answer choices to decimals as well, you can easily figure out which value is greater than \(\displaystyle 0.75\):

\(\displaystyle \frac{3}{5}=0.6< 0.75\)

\(\displaystyle \frac{5}{7}=0.71< 0.75\)

\(\displaystyle \frac{2}{3}=0.667< 0.75\)

\(\displaystyle \frac{3}{4}=0.75=0.75\)

\(\displaystyle \frac{7}{8}=0.875>0.75\), so \(\displaystyle \frac{7}{8}\) is the correct answer.

Example Question #1 : How To Add Fractions

Jesse has a large movie collection containing X movies. 1/3 of his movies are action movies, 3/5 of the remainder are comedies, and the rest are historical movies. How many historical movies does Jesse own?

Possible Answers:

(3/9)*X

(7/12)*X

(4/15)*X

(11/15)*X

(2/5)*X

Correct answer:

(4/15)*X

Explanation:

1/3 of the movies are action movies. 3/5 of 2/3 of the movies are comedies, or (3/5)*(2/3), or 6/15. Combining the comedies and the action movies (1/3 or 5/15), we get 11/15 of the movies being either action or comedy. Thus, 4/15 of the movies remain and all of them have to be historical.

Example Question #2 : How To Add Fractions

If x = 1/3 and y = 1/2, find the value of 2x + 3y.

Possible Answers:

2

5/6

13/6

6/5

1

Correct answer:

13/6

Explanation:

Substitute the values of x and y into the given expression:

2(1/3) + 3(1/2)

= 2/3 + 3/2

= 4/6 + 9/6

= 13/6

Example Question #131 : Arithmetic

Alternating1

Possible Answers:

\dpi{100} \frac{47}{60}\(\displaystyle \dpi{100} \frac{47}{60}\)

\dpi{100} -\frac{47}{60}\(\displaystyle \dpi{100} -\frac{47}{60}\)

\dpi{100} \frac{17}{60}\(\displaystyle \dpi{100} \frac{17}{60}\)

\dpi{100} -\frac{43}{60}\(\displaystyle \dpi{100} -\frac{43}{60}\)

\dpi{100} \frac{43}{60}\(\displaystyle \dpi{100} \frac{43}{60}\)

Correct answer:

\dpi{100} \frac{47}{60}\(\displaystyle \dpi{100} \frac{47}{60}\)

Explanation:

Alternating2

Alternating3

Example Question #612 : Arithmetic

What is the solution, reduced to its simplest form, for x = \frac{7}{9}+\frac{3}{5}+\frac{2}{15}+\frac{7}{45}}\(\displaystyle x = \frac{7}{9}+\frac{3}{5}+\frac{2}{15}+\frac{7}{45}}\) ?

Possible Answers:

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

x = \frac{115}{45}\(\displaystyle x = \frac{115}{45}\)

x = \frac{75}{45}\(\displaystyle x = \frac{75}{45}\)

x =2\(\displaystyle x =2\)

x = \frac{7}{15}\(\displaystyle x = \frac{7}{15}\)

Correct answer:

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

Explanation:

x=\frac{7}{9}+\frac{3}{5}+\frac{2}{15}+\frac{7}{45}=\frac{35}{45}+\frac{27}{45}+\frac{6}{45}+\frac{7}{45}=\frac{75}{45}=\frac{5}{3}\(\displaystyle x=\frac{7}{9}+\frac{3}{5}+\frac{2}{15}+\frac{7}{45}=\frac{35}{45}+\frac{27}{45}+\frac{6}{45}+\frac{7}{45}=\frac{75}{45}=\frac{5}{3}\)

Example Question #1 : How To Add Fractions

What is the result of adding \(\displaystyle 20\%\) of \(\displaystyle \frac{2}{7}\) to \(\displaystyle \frac{1}{4}\)?

Possible Answers:

\(\displaystyle \frac{3}{39}\)

\(\displaystyle \frac{23}{11}\)

\(\displaystyle \frac{47}{140}\)

\(\displaystyle \frac{43}{140}\)

\(\displaystyle \frac{3}{28}\)

Correct answer:

\(\displaystyle \frac{43}{140}\)

Explanation:

Let us first get our value for the percentage of the first fraction. 20% of 2/7 is found by multiplying 2/7 by 2/10 (or, simplified, 1/5): (2/7) * (1/5) = (2/35)

Our addition is therefore (2/35) + (1/4). There are no common factors, so the least common denominator will be 35 * 4 or 140. Multiply the numerator and denominator of 2/35 by 4/4 and the numerator of 1/4 by 35/35.

This yields:

(8/140) + (35/140)  = 43/140, which cannot be reduced.

Example Question #613 : Arithmetic

Add:

\(\displaystyle \frac{2}{9x}+\frac{4}{27}\)

Possible Answers:

\(\displaystyle \frac{10}{27x}\)

\(\displaystyle \frac{2x+6}{27x}\)

\(\displaystyle \frac{4x+6}{27}\)

\(\displaystyle \frac{4x+6}{27x}\)

\(\displaystyle \frac{6}{27x}\)

Correct answer:

\(\displaystyle \frac{4x+6}{27x}\)

Explanation:

Find the least common denominator to solve this problem

Multiply 27 with \(\displaystyle x\), and multiply \(\displaystyle 9x\) with 3 to obtain common denominators.

Convert the fractions.

\(\displaystyle \frac{2}{9x}+\frac{4}{27}=\frac{6}{27x}+\frac{4x}{27x}\)

Combine the terms as one fraction.

The answer is:  \(\displaystyle \frac{4x+6}{27x}\)

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