I have revised the free file that I posted on Monday for comparing groups. After using them in the classroom, I found a few glitches :) If you would like an updated version, click here. I have changed the orientation of a few of the numbers, so they are all consistent and so that they are suitable for beginning to teach groups of two.
Teaching the children to "see" the cards as groups of two will also help for when you want to start teaching odd and even numbers.
I used the large cards to model how to compare numbers. Hold two different number cards up and ask the students to tell you which card shows more. Then ask them to tell you how they could tell you how many more. Encourage a range of students to tell you how they would find out. Show the students how to hold up the two cards in front of one another to clearly show how many more squares are on one card. Repeat this a few times with a range of different cards.
Here is a worksheet to help your students consolidate their learning.