I Have Who Has cards are a great way to practice content skills, mental math and listening skills. It is one of the few whole group activities where it is mandatory that you participate all the time or it won't work.
In the beginning, give students time to build their number on their place value mat. When someone calls out their base ten block pieces, they'll be ready. When they become more proficient with place value, most of them won't need the blocks.
I use a stopwatch and time how long it takes us to get through the cards. The next time we do it, we try to beat our previous time.
Included in this set: 30 I Have Who Has cards