For teaching quantity and number association till 50 I used a toy train with an engine and two boogies. Write tens on the first boogie and units on the other one. Children had to put any number flash card e.g. 24 on the engine then using bead material of tens and units they have to place the correct number in the boogies e.g. two bar of tens in the first boogie and 4 units or individual beads in the other one. Let the children place different numbers flash cards on the engine and continue the activity.