Understand that the teen numbers (11–19) are composed of ten ones and some further ones (early place value)
You already know how to count and read numbers past ten. Now look closer at numbers like 11 to 19. Each teen number is one full ten, plus a few more ones.
Sam has 16 cubes. He puts ten cubes in one tower. Six cubes are left over. Ten and six make sixteen.
A teen number is written with two digits. The 1 in front does not mean one block. It stands for the whole ten. The digit after it counts the extra ones. In 16, the 1 is Sam's ten and the 6 is the six left over. You can write that as 16 = 10 + 6. The plus joins the parts, and both sides show the same number.
When you see a teen number, picture the ten as already made, then count only the extra ones. On a number line, jump straight to 10, then hop the extra ones. You never have to count from 1.
Every teen number is one ten and some more ones.
You can already read and write the numbers up to 20. Now look at what one of them is made of. Sam has 16 cubes in a pile.
Sam wants to snap some of his cubes into one full tower of ten. How many cubes go in that tower?
Jobs that lean on this skill. Follow one to see everything it is built on.
30 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.