Counting Objects to 20

Arithmetic · Axiom Academy

EXAMPLE Counting Objects to 20 Counting 17 objects step by step — grouping in fives makes a large count fast and reliable A collection of objects is laid out in rows of five, with a short final row. How many objects are there in all? Three full rows of five (blue) and a partial row of two (green). Nice work — you counted all 17 objects without losing track. Grouping turned a tedious one-by-one count into a few quick additions. Group in fives: a full row of five can be taken in at a glance, so you count groups instead of single objects. Skip count: the row totals run 5, 10, 15 , then two more — much faster than counting from 1 , and easier to check. Stay organized: moving row by row guarantees nothing is skipped or counted twice. Result: 5 + 5 + 5 + 2 = 17 objects in all. Another way to see it: 17 = 10 + 7 — one group of ten plus seven more. The same grouping idea scales up to counting hundreds and thousands.

This is the written version of the interactive lesson above. See the full Arithmetic course.