Introduction to Multiplication
Lessons in this chapter
About Introduction to Multiplication
Multiplication Magic is the biggest new idea of 2nd grade: a fourth operation, built out of the repeated addition kids have been doing all year.
Multiply by Grouping and Arrays establishes what multiplication means before any table is learned. Four groups of three, and a rectangle of four rows by three columns, both give twelve, and the array is the better picture because it shows immediately why 4 × 3 and 3 × 4 match.
Build Multiplication Tables of 2, 5 and 10 starts with the tables kids already have from skip counting, so the first tables feel like something they knew rather than something new. Build Multiplication Tables of 3 and 4 then adds the two that have to be built.
Solve Contextual Problems on Multiplication puts it into situations. The signal to look for is equal groups: five bags with four apples in each is multiplication, while five apples and four more is not, and telling those apart is the real skill.
Multiply by Grouping and Arrays, Build Multiplication Tables of 2, 5 and 10 and Build Multiplication Tables of 3 and 4 each open as a worksheet in the page, marked question by question. The table lessons are the times tables practice most second graders need, and the array lesson is what makes the tables mean something. Four lessons, all free.
Frequently asked questions
Multiplying by making equal groups and arrays, then building the tables of 2, 5 and 10, then 3 and 4, and finally word problems set in context. Arrays come first so that a table is a shortcut for something a child has already counted. The array and repeated addition work sits in Operations and Algebraic Thinking (2.OA); the tables themselves are formally a 3rd grade target in 3.OA, taught here because the groundwork is ready.
Adding equal groups. Four groups of three is 4 × 3, which is 3 + 3 + 3 + 3. The equal part is what makes it multiplication rather than addition.
Objects arranged in rows and columns. A 4 by 3 array shows 4 × 3 at a glance, and turning it on its side shows why 4 × 3 and 3 × 4 give the same answer.
2, 5 and 10 first, since skip counting already gives them, then 3 and 4.
They are the same thing. Counting 3, 6, 9, 12 is the three times table in sequence form, which is why skip counting comes earlier in the year.
Look for equal groups. Five bags with four apples each is multiplication; five apples and four more apples is addition.