I love posing questions to my students like this one and having them share their thinking. We did two today during math time. They love it and I love it!
It is a good transitioning strategy too. Today I told my students to take out one sticky note, then I posed the question. They were to answer the question, then on their way down the carpet for our lesson, they were to post their answer.
I can quickly look through and see who is understanding things and who isn't. We did the first one to start the lesson today, to activate some knowledge and for me to quickly see if they were understanding our current skills. Then I did the other one after our lesson to see how well they were understanding how to find the missing number.