Common Core: 2nd Grade Math : Operations & Algebraic Thinking

Study concepts, example questions & explanations for Common Core: 2nd Grade Math

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Example Questions

Example Question #91 : How To Subtract

\(\displaystyle \frac{\begin{array}[b]{r}20\\ -\ 1\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle 18\)

\(\displaystyle 19\)

\(\displaystyle 17\)

\(\displaystyle 15\)

Correct answer:

\(\displaystyle 19\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 20\) and count back \(\displaystyle 1.\)

\(\displaystyle 20,19\)

\(\displaystyle \frac{\begin{array}[b]{r}20\\ -\ 1\end{array}}{ \ \ \space19}\)

Example Question #311 : Numbers And Operations

\(\displaystyle \frac{\begin{array}[b]{r}19\\ -\ 2\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 14\)

\(\displaystyle 17\)

\(\displaystyle 16\)

\(\displaystyle 18\)

\(\displaystyle 15\)

Correct answer:

\(\displaystyle 17\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 19\) and count back \(\displaystyle 2.\)

\(\displaystyle 19,18,17\)

\(\displaystyle \frac{\begin{array}[b]{r}19\\ -\ 2\end{array}}{ \ \ \space17}\)

Example Question #1 : Operations & Algebraic Thinking

Solve the following: 

\(\displaystyle \frac{\begin{array}[b]{r}16\\ -\ 14\end{array}}{ \ \ \ \space}\)

Possible Answers:

\(\displaystyle 3\)

\(\displaystyle 4\)

\(\displaystyle 5\)

\(\displaystyle 2\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 2\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 16\) and count back \(\displaystyle 14.\)

\(\displaystyle 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2\)

\(\displaystyle \frac{\begin{array}[b]{r}16\\ -\ 14\end{array}}{ \ \ \ \ \ \space2}\)

Example Question #1 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}13\\ -\ 6\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 5\)

\(\displaystyle 9\)

\(\displaystyle 6\)

\(\displaystyle 7\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 7\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 13\) and count back \(\displaystyle 6\).

\(\displaystyle 13, 12, 11, 10, 9, 8, 7\)

\(\displaystyle \frac{\begin{array}[b]{r}13\\ -\ 6\end{array}}{ \ \ \ \space7}\)

Example Question #3 : Mentally Add And Subtract Within 20: Ccss.Math.Content.2.Oa.B.2

\(\displaystyle \frac{\begin{array}[b]{r}9\\ -\ 3\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle 7\)

\(\displaystyle 6\)

\(\displaystyle 5\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 6\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 9\) and count back \(\displaystyle 3\).

\(\displaystyle 9, 8, 7, 6\)

\(\displaystyle \frac{\begin{array}[b]{r}9\\ -\ 3\end{array}}{ \ \ \ \space6}\)

Example Question #1 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}7\\ -\ 7\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle 7\)

\(\displaystyle 3\)

\(\displaystyle 0\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle 0\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 7\) and count back \(\displaystyle 7\).

\(\displaystyle 7, 6, 5, 4, 3, 2, 1, 0\)

\(\displaystyle \frac{\begin{array}[b]{r}7\\ -\ 7\end{array}}{ \ \ \ \space0}\)

Example Question #2 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}6\\ -\ 5\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle 2\)

\(\displaystyle 5\)

\(\displaystyle 0\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle 1\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 6\) and count back \(\displaystyle 5\).

\(\displaystyle 6, 5, 4, 3, 2, 1\)

\(\displaystyle \frac{\begin{array}[b]{r}6\\ -\ 5\end{array}}{ \ \ \ \space1}\)

Example Question #2 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}5\\ -\ 3\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 0\)

\(\displaystyle 2\)

\(\displaystyle 4\)

\(\displaystyle 5\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle 2\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 5\) and count back \(\displaystyle 3\).

\(\displaystyle 5, 4, 3, 2\)

\(\displaystyle \frac{\begin{array}[b]{r}5\\ -\ 3\end{array}}{ \ \ \ \space2}\)

Example Question #101 : How To Subtract

\(\displaystyle \frac{\begin{array}[b]{r}4\\ -\ 1\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 0\)

\(\displaystyle 3\)

\(\displaystyle 5\)

\(\displaystyle 4\)

\(\displaystyle 2\)

Correct answer:

\(\displaystyle 3\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 4\) and count back \(\displaystyle 1.\)

\(\displaystyle 4, 3\)

\(\displaystyle \frac{\begin{array}[b]{r}4\\ -\ 1\end{array}}{ \ \ \ \space3}\)

Example Question #321 : Numbers And Operations

\(\displaystyle \frac{\begin{array}[b]{r}7\\ -\ 2\end{array}}{ \ \ \ \space?}\)

Possible Answers:

\(\displaystyle 3\)

\(\displaystyle 6\)

\(\displaystyle 2\)

\(\displaystyle 5\)

\(\displaystyle 4\)

Correct answer:

\(\displaystyle 5\)

Explanation:

To subtract we can count backwards. Start at \(\displaystyle 7\) and count back \(\displaystyle 2\).

\(\displaystyle 7, 6, 5\)

\(\displaystyle \frac{\begin{array}[b]{r}7\\ -\ 2\end{array}}{ \ \ \ \space5}\)

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