Long and Short - Long and Short

Convert $7\text{ m } 45\text{ cm}$ into centimeters.

$7 \times 100\text{ cm} + 45\text{ cm} = 700\text{ cm} + 45\text{ cm} = 745\text{ cm}$

Since $1\text{ m} = 100\text{ cm}$, we multiply $7$ by $100$ to get $700\text{ cm}$ and then add the remaining $45\text{ cm}$.

Reena's school is $5\text{ km } 200\text{ m}$ away from her house. She has traveled $2\text{ km } 800\text{ m}$. How much distance is left?

$\begin{array}{r} 5\text{ km } 200\text{ m} \\ - 2\text{ km } 800\text{ m} \\ \hline 2\text{ km } 400\text{ m} \end{array}$

We subtract the distance traveled from the total distance. Since $800$ is larger than $200$, we borrow $1\text{ km}$ ($1000\text{ m}$) from the $5\text{ km}$ column. So, $1000 + 200 = 1200\text{ m}$. Then $1200 - 800 = 400\text{ m}$ and $4 - 2 = 2\text{ km}$.

Add $12\text{ m } 50\text{ cm}$ and $8\text{ m } 75\text{ cm}$.

$\begin{array}{r} 12\text{ m } 50\text{ cm} \\ + 8\text{ m } 75\text{ cm} \\ \hline 21\text{ m } 25\text{ cm} \end{array}$

First, add the centimeters: $50 + 75 = 125\text{ cm}$. Since $100\text{ cm} = 1\text{ m}$, we write $25$ in the $cm$ column and carry over $1\text{ m}$ to the $m$ column. Then, $12 + 8 + 1 = 21\text{ m}$.