Teen numbers (ten and some ones) Knowledge-Based Study

Study notes

1. What is a Teen Number?

   Teen numbers are the numbers from 11 through 19.

   Every teen number is made of one full group of ten and some extra ones.

   • A full group of ten is written as 10.
   • When we add single units (ones) to 10, we make a teen number.

   Ten and Extra Ones

   We can break apart any teen number into a group of 10 plus more ones:

   • 11 is 10 and 1 one ($10 + 1 = 11$)
   • 12 is 10 and 2 ones ($10 + 2 = 12$)
   • 13 is 10 and 3 ones ($10 + 3 = 13$)
   • 14 is 10 and 4 ones ($10 + 4 = 14$)
   • 15 is 10 and 5 ones ($10 + 5 = 15$)

   Notice that the group of ten stays the same, while the number of extra ones changes.

   Reading the Digits

   Look at the number 16:

   • The digit on the left, 1, tells us there is 1 ten (a group of 10).
   • The digit on the right, 6, tells us there are 6 ones.

   Therefore, 16 means $10 + 6$.

   Let us look at the remaining teen numbers:

   • 17 is 1 ten and 7 ones ($10 + 7 = 17$)
   • 18 is 1 ten and 8 ones ($10 + 8 = 18$)
   • 19 is 1 ten and 9 ones ($10 + 9 = 19$)

   Key Takeaways

   Remember this simple rule for all teen numbers from 11 to 19:

   Teen Number = 10 + Ones

   Whenever you see a two-digit number starting with 1, you can instantly see that it holds one whole bundle of ten and a set of single units.