3. Two digits

(1), we often meet ten objects as a whole in our life. In fact, 10 one is ten, and 1 10 is 10 one.

For example, 15 contains (1) tens and (5) ones, and 15 contains (15) ones.

(2) On the counter, the first digit from the right is the number of digits. The second place is: ten. A bead on the cell indicates: 1 cell; A bead on the tenth digit means: 1 tenth digit.

(3) Read 1 1, 12, 13, 14, 15 before writing.

For example: 15, read: 15 and write: 15.