Multi-Digit Multiplication

Learn to multiply larger numbers using the standard algorithm

Multiplying by One Digit

Example: $23 \times 4$

&23 \\ \times &\phantom{0}4 \\ \hline &92 \end{align}$$ Steps: 1. Multiply ones: $3 \times 4 = 12$ (write 2, carry 1) 2. Multiply tens: $2 \times 4 = 8$, plus carried 1 = 9 ## Multiplying by Two Digits **Example:** $25 \times 13$ $$\begin{align} &\phantom{0}25 \\ \times &\phantom{0}13 \\ \hline &\phantom{0}75 & \text{(25 × 3)} \\ + &250 & \text{(25 × 10)} \\ \hline &325 \end{align}$$ ## Tips to Remember - Line up your numbers carefully - Remember to add a zero when multiplying by the tens place - Check your work by estimating ## Real-World Uses - Calculating total cost (items × price) - Finding area (length × width) - Figuring out groups of things

Calculate: $34 \times 5$

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Solution:

&34 \\ \times &\phantom{0}5 \\ \hline &170 \end{align}$$ Step by step: - $4 \times 5 = 20$ (write 0, carry 2) - $3 \times 5 = 15$, plus carried 2 = 17 **Answer:** 170

A box contains 24 crayons. If there are 6 boxes, how many total crayons are there?

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Solution:

Multiply: $24 \times 6$

&24 \\ \times &\phantom{0}6 \\ \hline &144 \end{align}$$ **Answer:** 144 crayons

Calculate: $46 \times 23$

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Solution:

&\phantom{0}46 \\ \times &\phantom{0}23 \\ \hline &138 & \text{(46 × 3)} \\ + &920 & \text{(46 × 20)} \\ \hline &1058 \end{align}$$ **Answer:** 1,058

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