Count to 100 by ones and by tens.
Count to 100 by ones. Start with the hundreds chart, then gradually move away from it. Conclude by giving your students the following puzzle, which is from Gardner's Entertaining Mathematical Puzzles:
Ten red socks and ten blue socks are all mixed up in a dresser drawer. The twenty socks are exactly alike except for their color. The room is in pitch darkness and you want two matching socks. What is the smallest number of socks you must take out of the drawer in order to be certain that you have a pair that match?
If students cannot figure it out, act out the problem as a class. For example, you could have a bag of twenty marbles, ten white and ten black. Have students draw from the bag until they get a matching pair. Running this experiment a few times, they will see maximum number of draws necessary is three. Then you can explain why.