and Subtraction is one of three yearlong resource guides in Contexts for Learning Mathematics Investigating Number Sense, Addition, and Subtraction (K3) Minilessons for Early Addition and Subtraction is a resource of 78 minilessons that you can choose from throughout the year. In contrast to investigations, which constitute the heart of the math workshop, the minilesson is more guided and more explicit, designed to be used at the start of math workshop and to last ten to fifteen minutes. Each day, no matter what other materials you are using, you might choose a minilesson from this resource to provide your students with experiences to develop efficient computation. You can also use the minilessons with small groups of students as you differentiate instruction. The minilessons in this guide were designed to be used in grades 12. Some of the minilessons make use of quick images with pictures. We call these billboards. They are carefully designed pictures that support the development of important strategies for addition and subtraction by building in potentially realizable strategies or constraints. Flashed for only a few seconds, they encourage children to give up trying to count each item and instead to use their natural ability to subitizeto perceive small amounts (such as 2, 3, or 4) as units and use them. In this way, children are supported to count on, skip-count, use doubles, and make use of the five-structure. Other minilessons in this resource unit make use of the arithmetic rack. Still others use ten-frames and coins (such as dimes and quarters) to encourage children to recognize and use landmark numbers (tens and twenty-fives) as they calculate. No matter which tool is usedbillboards, the arithmetic rack, ten-frames, or coinseach minilesson is crafted as a tightly structured series, or string, of computation problems designed to encourage children to look to the numbers first, before they decide on a computation strategy. The strings are likely to generate discussion of certain strategies or big ideas underlying an understanding of early number sense, addition, and subtraction. To learn more visit http: //www.contextsforlearning.com