Common Core: 3rd Grade Math : Operations & Algebraic Thinking

Study concepts, example questions & explanations for Common Core: 3rd Grade Math

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Example Questions

Example Question #131 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}12\\ \times 9\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 144\)

\(\displaystyle 108\)

\(\displaystyle 120\)

\(\displaystyle 96\)

\(\displaystyle 132\)

Correct answer:

\(\displaystyle 108\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 12\times9\) means adding \(\displaystyle 9\) twelve times. 

\(\displaystyle 9+9+9+9+9+9+9+9+9+9+9+9=108\) and \(\displaystyle 12\times9=108\)

Or we can think of this as grouping objects. We have \(\displaystyle 12\) groups, with \(\displaystyle 9\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #132 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}4\\ \times 2\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle 8\)

\(\displaystyle 20\)

\(\displaystyle 16\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 8\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 4\times2\) means adding \(\displaystyle 2\) four times. 

\(\displaystyle 2+2+2+2=8\) and \(\displaystyle 4\times2=8\)

Or we can think of this as grouping objects. We have \(\displaystyle 4\) groups, with \(\displaystyle 2\) objects in each group. We can count up the total number of objects, in this case triangles. 

Screen shot 2015 08 17 at 9.04.25 pmScreen shot 2015 08 17 at 9.04.25 pm

Example Question #133 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}10\\ \times 3\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 30\)

\(\displaystyle 20\)

\(\displaystyle 50\)

\(\displaystyle 40\)

\(\displaystyle 60\)

Correct answer:

\(\displaystyle 30\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 10\times3\) means adding \(\displaystyle 3\) ten times. 

\(\displaystyle 3+3+3+3+3+3+3+3+3+3=30\) and \(\displaystyle 10\times3=30\)

Or we can think of this as grouping objects. We have \(\displaystyle 10\) groups, with \(\displaystyle 3\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #134 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}8\\ \times 4\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 48\)

\(\displaystyle 32\)

\(\displaystyle 40\)

\(\displaystyle 64\)

\(\displaystyle 56\)

Correct answer:

\(\displaystyle 32\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 8\times4\) means adding \(\displaystyle 4\) six times. 

\(\displaystyle 4+4+4+4+4+4+4+4=32\) and \(\displaystyle 8\times4=32\)

Or we can think of this as grouping objects. We have \(\displaystyle 8\) groups, with \(\displaystyle 4\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #135 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}2\\ \times 6\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 24\)

\(\displaystyle 36\)

\(\displaystyle 30\)

\(\displaystyle 12\)

\(\displaystyle 18\)

Correct answer:

\(\displaystyle 12\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 2\times6\) means adding \(\displaystyle 6\) two times. 

\(\displaystyle 6+6=12\) and \(\displaystyle 2\times6=12\)

 

Or we can think of this as grouping objects. We have \(\displaystyle 2\) groups, with \(\displaystyle 6\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #136 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}5\\ \times 8\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 30\)

\(\displaystyle 25\)

\(\displaystyle 35\)

\(\displaystyle 45\)

\(\displaystyle 40\)

Correct answer:

\(\displaystyle 40\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 5\times8\) means adding \(\displaystyle 8\) five times. 

\(\displaystyle 8+8+8+8+8=40\) and \(\displaystyle 5\times8=40\)

Or we can think of this as grouping objects. We have \(\displaystyle 5\) groups, with \(\displaystyle 8\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #137 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}5\\ \times 4\end{array}}{ \ \ \ \space}\)

 

 

Possible Answers:

\(\displaystyle 20\)

\(\displaystyle 15\)

\(\displaystyle 5\)

\(\displaystyle 25\)

\(\displaystyle 10\)

Correct answer:

\(\displaystyle 20\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 5\times4\) means adding \(\displaystyle 4\) five times. 

\(\displaystyle 4+4+4+4+4=20\) and \(\displaystyle 5\times4=20\)

Or we can think of this as grouping objects. We have \(\displaystyle 5\) groups, with \(\displaystyle 4\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #138 : Operations & Algebraic Thinking

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

 

Possible Answers:

\(\displaystyle 14\)

\(\displaystyle 7\)

\(\displaystyle 21\)

\(\displaystyle 35\)

\(\displaystyle 28\)

Correct answer:

\(\displaystyle 14\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 7\times2\) means adding \(\displaystyle 2\) seven times. 

\(\displaystyle 2+2+2+2+2+2+2=14\) and \(\displaystyle 7\times2=14\)

Or we can think of this as grouping objects. We have \(\displaystyle 7\) groups, with \(\displaystyle 2\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #139 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}10\\ \times 2\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 10\)

\(\displaystyle 20\)

\(\displaystyle 30\)

\(\displaystyle 40\)

\(\displaystyle 50\)

Correct answer:

\(\displaystyle 20\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 10\times2\) means adding \(\displaystyle 2\) ten times. 

\(\displaystyle 2+2+2+2+2+2+2+2+2+2=20\) and \(\displaystyle 10\times2=20\)

Or we can think of this as grouping objects. We have \(\displaystyle 10\) groups, with \(\displaystyle 2\) objects in each group. We can count up the total number of objects, in this case triangles. 

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Example Question #140 : Operations & Algebraic Thinking

\(\displaystyle \frac{\begin{array}[b]{r}9\\ \times 12\end{array}}{ \ \ \ \space}\)

 

Possible Answers:

\(\displaystyle 99\)

\(\displaystyle 90\)

\(\displaystyle 72\)

\(\displaystyle 81\)

\(\displaystyle 108\)

Correct answer:

\(\displaystyle 108\)

Explanation:

Multiplication can be thought of as repeated addition, or as objects in a group. 

\(\displaystyle 9\times12\) means adding \(\displaystyle 12\) nine times. 

\(\displaystyle 12+12+12+12+12+12+12+12+12=108\) and \(\displaystyle 12\times9=108\)

Or we can think of this as grouping objects. We have \(\displaystyle 9\) groups, with \(\displaystyle 12\) objects in each group. We can count up the total number of objects, in this case triangles.

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