Letâs find a pattern as we count from 11 to 20! Join Mr. Hammer for Lesson 11 (omit Lesson 10) as we show, count, and write numbers from 11 to 20 in towers increasing by 1. For this lesson, youâll need 20 objects that you can count and move around as well as a pencil and paper. If you have access to a printer, we also suggest accessing the Problem Set and Sentence Frame using the links below the video.