There are two quick and easy ways to add 9:
Because 9 is close to 10, adding is easy with a little thinking. First, revise with students the place value idea that 10 plus some ones is an easy question, and will be a “teen” number. Introduce students to two strategies:
As the video explains, the main thing is not to teach a required set of steps, or algorithm, but to help students figure out for themselves how 9 being next to 10 makes adding 9 an easy mental process. Ultimately, as with all number facts or times tables, students need to “just know” the answers, having committed them to memory.