SAT II Math I : SAT Subject Test in Math I

Study concepts, example questions & explanations for SAT II Math I

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Example Questions

Example Question #51 : Sat Subject Test In Math I

How many elements are in a set that has exactly 128 subsets?

Possible Answers:

\(\displaystyle 16\)

None of the other responses is correct.

\(\displaystyle 8\)

\(\displaystyle 7\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 7\)

Explanation:

A set with \(\displaystyle N\) elements has \(\displaystyle 2 ^{N}\) subsets.

Solve:

\(\displaystyle 2 ^{N} = 128\)

\(\displaystyle \ln 2 ^{N} = \ln 128\)

\(\displaystyle N \ln 2 = \ln 128\)

\(\displaystyle N = \frac{\ln 128}{\ln 2} = \frac{4.8520 }{0.6931} = 7\)

Example Question #1 : Mathematical Relationships

Rewrite as a single logarithmic expression:

\(\displaystyle \ln x - 2 \ln (x + 2)\)

Possible Answers:

\(\displaystyle \ln \frac{1}{x^{2} +3x +4}\)

\(\displaystyle \ln \frac{x}{2x + 4}\)

\(\displaystyle \ln \frac{1}{x +4}\)

\(\displaystyle \ln \frac{x}{x^{2} +4x + 4}\)

\(\displaystyle \ln \left (-x^{2} -3x -4 \right )\)

Correct answer:

\(\displaystyle \ln \frac{x}{x^{2} +4x + 4}\)

Explanation:

Using the properties of logarithms

\(\displaystyle n \ln a = \ln a^{n}\) and \(\displaystyle \ln a - \ln b = \ln \frac{a}{b}\),

we simplify as follows:

 

\(\displaystyle \ln x - 2 \ln (x + 2)\)

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

\(\displaystyle = \ln x - \ln (x^{2} +4x + 4)\)

\(\displaystyle = \ln \frac{x}{x^{2} +4x + 4}\)

Example Question #1 : Exponents And Logarithms

Solve:  \(\displaystyle log_{3}27\)

Possible Answers:

\(\displaystyle 9\)

\(\displaystyle 27\)

\(\displaystyle \frac{1}{9}\)

\(\displaystyle 30\)

\(\displaystyle 3\)

Correct answer:

\(\displaystyle 3\)

Explanation:

In order to solve this problem, covert 27 to the correct base and power.

\(\displaystyle log_{3}27 = log_{3}\: 3^3\)

Since \(\displaystyle log_xx^n = n\), the correct answer is \(\displaystyle 3\).

Example Question #51 : Sat Subject Test In Math I

Simplify \(\displaystyle (x^{-4})^7\)

Possible Answers:

\(\displaystyle x^{\frac{7}{4}}\)

\(\displaystyle x^3\)

\(\displaystyle x^{-11}\)

\(\displaystyle x^{-47}\)

\(\displaystyle x^{-28}\)

Correct answer:

\(\displaystyle x^{-28}\)

Explanation:

When an exponent is raised by another exponent, we just multiply the powers.

\(\displaystyle (x^{-4})^7=x^{-4*7}=x^{-28}\)

Example Question #2 : Exponents And Logarithms

Simplify:

\(\displaystyle 3^9+3^9+3^9\)

Possible Answers:

\(\displaystyle 3^{27}\)

\(\displaystyle 9^9\)

\(\displaystyle 9^{27}\)

\(\displaystyle 3^{10}\)

\(\displaystyle 27^{9}\)

Correct answer:

\(\displaystyle 3^{10}\)

Explanation:

When adding exponents, we don't add the exponents or multiply out the bases. Our goal is to see if we can factor anything. We do see three \(\displaystyle 3^9\). Let's factor.

\(\displaystyle 3^9+3^9+3^9=3^9(1+1+1)=3^9(3)=3^{10}\) Remember when multiplying exponents, we just add the powers.

 

Example Question #54 : Sat Subject Test In Math I

Solve and simplify.

\(\displaystyle \sqrt[3]{125}\)

Possible Answers:

\(\displaystyle 5\sqrt{5}\)

\(\displaystyle 25\)

\(\displaystyle 5\)

\(\displaystyle 5\sqrt[3]{5}\)

\(\displaystyle 3\)

Correct answer:

\(\displaystyle 5\)

Explanation:

\(\displaystyle \sqrt[3]{125}\) Another way to write this is \(\displaystyle x^3=125\). The only number that makes \(\displaystyle 125\) is \(\displaystyle 5^3\)

Example Question #55 : Sat Subject Test In Math I

Simplify:

\(\displaystyle \log_3729\)

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle 243\)

\(\displaystyle 9\)

\(\displaystyle 3^{729}\)

\(\displaystyle 3^9\)

Correct answer:

\(\displaystyle 6\)

Explanation:

\(\displaystyle \log_3729\) is the same as \(\displaystyle 3^x=729\). Let's factor out \(\displaystyle 729\). It's the same as \(\displaystyle 3^6\). Therefore \(\displaystyle x=6\) which is the answer to our question.

Example Question #52 : Sat Subject Test In Math I

Simplify:

\(\displaystyle \log50-\log5\)

Possible Answers:

\(\displaystyle \log45\)

\(\displaystyle \log250\)

\(\displaystyle 5\log50\)

\(\displaystyle 0\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle 1\)

Explanation:

When dealing with subtraction in regards to logarithms, it's the same as dividing the numbers.

\(\displaystyle \log50-\log5=\frac{\log50}{\log5}=\log \frac{50}{5}=\log10=1\)

Example Question #53 : Sat Subject Test In Math I

Simplify:

\(\displaystyle \log_618+\log_672\)

 

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle 3\log_618\)

\(\displaystyle 6\log90\)

\(\displaystyle \log_690\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 4\)

Explanation:

When dealing with addition in regards to logarithms, it's the same as multiplying the numbers.

\(\displaystyle \log_618+\log_672=\log_6(18*72)=\log_61296=4\)

Example Question #58 : Sat Subject Test In Math I

Solve: \(\displaystyle (x^{2})^{5}\) when \(\displaystyle x=2\).

Possible Answers:

\(\displaystyle 1024\)

\(\displaystyle 100\)

\(\displaystyle 1000\)

\(\displaystyle 20\)

\(\displaystyle 64\)

Correct answer:

\(\displaystyle 1024\)

Explanation:

Power rule says when an exponent is raised to another exponent, you must multiply the exponents.  

So \(\displaystyle 2*5=10\) and our expression is now \(\displaystyle x^{10}\).  

Plug in the given value to get 

\(\displaystyle 2^{10}=1024\).

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