### Math 247 Unit 2: Base 10 numbers and algorithms

#### Section 7: Multiplication and division algorithms.

**Goal:** The goals this week are for you to

- Know some ways of mentally computing with 2 digit numbers

- Know some common alternate and scaffolding algorithms for
multiplication and division

- Know how to show the standard algorithms for multiplication and
division using manipulatives and make connections between
manipulatives and the pencil and paper work.

**Resources**

**Assignments:** Please scan as necessary, and put all
assignments in the dropbox.
**Multiplication**

Paths to the standard algorithm:

Read and watch this discussion of breaking down multidigit multiplication using arrays and the distributive law, and recording multiplication using the expanded and the standard algorithm. (note: this page includes links to several videos, and hence is longer than it appears).

Assignment 25: Expanded and standard algorithms assignment (All assigments due July 12)

Mental math and the lattice algorithm:

Read and watch this discussion of mental multiplication strategies and the lattice algorithm.

Assignment 26: Mental arithmetic multiplication and the lattice algorithm

Error patterns July 9

Assignment 27: Figure out the error
patterns and identify the alternate algorithms in the assignment
D2L->Content->Assignments-> Multiplication error
patterns and algorithms

**Division**

**Partitive division and long division**

**Do first**: open the base 10 blocks Smart notebook (see resources), and use them to divide 860 ÷ 6 using a partitive interpretation (make 6 groups)

Watch:

Assignment 28: Manipulatives and partitive long division assignment (video)

**Measurement division and the scaffolding algorithm**

Watch:

Assignment:

Assignment 29: Scaffolding division assignment

**Why can't you divide by 0?**

Watch:

Read: Bassarear 4th ed pg 193 (3rd ed. pg. 188)

Assignment:

Assn 30: Write or record on video a good
explanation of
why you can't divide 10 by 0.

**Error patterns**

Watch:

Assignment 31: Do the assignment "division error patterns and
algorithms"
on D2L->content->assignments. (print, do, scan, dropbox)

July
12