Write down the answers using digits:

10+1=11 (eleven) 15+1=16 (sixteen)   

11+1=12 (twelve) 16+1=17 (seventeen)   

12+1=13 (thirteen) 17+1=18 (eighteen)

13+1=14 (fourteen) 18+1=19 (nineteen)

14+1=15 (fifteen) 19+1=20 (twenty)  

Use this line to find out the sequence of numbers: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20

Back to practice

Look at the numbers: 1 2 3 4 5 6 7 8 9 10. Which number is different from the others? It is the number 10. It consists of two signs - 1 and 0. Zero designates the empty place. What happens if you put other signs in the place of zero after the number one? Let's see: 11 12 13 14 15 16 17 18 19. We get new numbers. Why do they contain two signs, and what does it mean? Let's figure it out.

Here are ten matches.

Let's combine them into one bundle.

It is the first ten. We denote it by the number 10. Let's put one match next to it. 

How many matches are there? Ten and one. This number is eleven - 11. We put another match.

How many is it? Ten and two. It is the number twelve - 12. Let's add one more match.

How many matches do we have now? Ten and three. Thirteen - 13.

We follow the same way when forming numbers from 1 to 10. We add one match to get a new number:

10+1=11 (eleven) 15+1=16 (sixteen) 

11+1=12 (twelve) 16+1=17 (seventeen) 

12+1=13 (thirteen) 17+1=18 (eighteen)  

13+1=14 (fourteen) 18+1=19 (nineteen)  

14+1=15 (fifteen) 19+1=20 (twenty)   

The first digit of given numbers is always 1. It doesn't change. We use it to designate the first ten objects. These are ten matches that we have grouped into one bundle. What do the numbers to the right of 1 mean? It is the number of single matches that we added to one bundle. In other words, 1 is the number of tens, the number on the right is the number of ones. Knowing this, what can you say about the number 20? The first digit is 2. It means there are two tens or two bundles of 10 matches in each. Zero indicates that there are no single matches next to these bundles. It is a zero unit.

All these numbers are greater than the number 10. On the number line, we can find them on the right of it: 10_11_12_13_14_15_16_17_18_19_20

The counting rules for numbers after ten do not change. We should count each item only once and don't miss a single one.

Back to practice