Some of my best ideas happen very spur of the moment. I'm sure since you are all teachers, you know exactly what I mean. You have one thing in your plan book and then your students ask a question and everything shifts instantly. I think out of all the lessons I plan, those are my favorite.
Fortunately, last year I had bagged them up so that each student could get a bag and it would have enough pieces for any problem from 1 to 99. If you haven't done this, it is a must. It saves SO much time and saving time definitely helps with classroom management.
After I passed out the bags, we went over our rules. There aren't many, but it's important to tell your kids up front what your expectations are.
2. No talking. I like to do what I call hotdog/hamburger. Every other student is a hotdog or a hamburger. This keeps kids from copying the kid next to them. However, it also means we have to be quiet or we don't hear our numbers.
That's it - two rules. However, if they break the rules, I take their items away and they have to sit and watch or write their spelling words two times before they can rejoin. It usually only takes one or two students losing the privilege and everyone else falls in line.
Here are some pictures I took during our lesson. My lower students started by just writing the number and showing me in rods and units. My higher students had to also show me the answer in expanded form.
So, the next time you need a quick hands-on math activity or lesson, this is an easy one that requires very little planning and should use materials you already have in your classroom.