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1-79.

For each number of pennies below, arrange them first into a complete rectangular array and then into a different rectangular array that has a remainder of one (so there is one extra penny). Write an expression for each arrangement.

1. $10$ pennies

Try dividing $10$ by one or two to get your rectangle.

$\begin{array} {c c c c c} \bigcirc & \bigcirc & \bigcirc & \bigcirc & \bigcirc\\ \bigcirc & \bigcirc & \bigcirc & \bigcirc & \bigcirc\\ \end{array}$

To have a remainder of one, you want your rectangular array to be one less than $10$. That means you need to use the factors of 9 to get a rectangle for it.

$\begin{array} {c c c c} \bigcirc & \bigcirc & \bigcirc\\ \bigcirc & \bigcirc & \bigcirc & \bigcirc\\ \bigcirc & \bigcirc & \bigcirc\\ \end{array}$

2. $15$ pennies

This one is very similar to the previous problem. What numbers divide into 15 evenly?

3. $25$ pennies

This problem is very similar to the previous two. What numbers divide into 25 evenly?