Tens boards: US version

Tens boards: US version hold the tens from 10 to 90, and a strip of unit numerals slides over the zero to turn 20 into 21, 22 and on to 29. The child hears the number name, builds it and counts out the matching quantity, so counting past ten stops being a rhyme and becomes a rule. Because the ten stays in view while only the unit changes, the pattern behind the number names is seen rather than explained, and counting carries on to ninety-nine. The second step after the boards for eleven to nineteen, for children from three years.