Background

“Teen” numbers can be very troublesome for some students because they do not realise that “teen” means 10, and the usual rule of saying tens before ones is broken. For example, sixteen means literally “six and ten”, which really should be “ten and six”. Also 11 and 12 break the “teen” pattern by not being “oneteen” and “twoteen”. Further confusion can occur for the students who fail to realise words ending in “ty” are tens. In particular, many students confuse “sixty” with “sixteen”. Persistence in teaching “teen” and “ty” is needed in overcoming these problems as understanding these numbers is essential by the time part-whole thinking emerges.

Activity – “Teen” Numbers

Seat the students in pairs. One partner shows 10 fingers. The other partner shows any number of fingers from one to nine, say six. The “ones” person says “six” and the other partner says “10”, and together they say “is sixteen”.

As a class, record teen numbers as equations on the board or modelling book, and get the students to read them out loud. For example 10 + 4 = 14 is on the board or modelling book. The students say “Ten and four is the same as (equals) 14.”

Activity – “Teen” Numbers

In pairs, one student points to a number between 10 and 20 on the hundreds board and the other student reads the number. Then together they show that many fingers. Repeat with the roles reversed.

Activity – “Teen” Numbers

On the Slavonic abacus, push across 10 beads on the first row, and then push across extra beads for any amount from 11 to 19, to allow the students to practise recalling the “teen” number facts.

Activity – “Ty” Words

Screen a Slavonic abacus from the students’ view while you move complete rows of 10. Turn the abacus around and ask the students to tell you how many beads they can see. Link the number of tens to the structure of the word, for example, “eight tens is eighty”, and its numeral on the hundreds board, for example, 80.

Activity –”Teen” and “Ty” Bingo

Every student has a hundreds board and eight transparent counters. Each student places transparent counters on any eight “teen” and “ty” numbers of their choice. You show a succession of “teen” and “ty” numbers on the Slavonic abacus. If any student has a counter on the matching number, they remove that counter. The first player to remove all their counters wins.