September 22, 2010

LookUsing a Ten Structure to Solve an Addition Problem

 

pg 52 of Beckman activity manualing at examples of students solving an addition problem using Ten Structure pictures

• Students #1 and 2 get it.  They understand how to group numbers and "carry" to the next place value.
• Student #3 - may not fully understand place value, and doesn't understand "changing out"  will struggle when moves on to subtraction.

Subtraction

How can we represent subtraction so students understand?

• 2+__=7 - student will subtract 2 from 7.....or count up
• Students need to understand fact families

• Number bond idea  

A misconception that a lot of student have is that addition and multiplication ALWAYS make numbers bigger.  NOT TRUE....not when you are adding or multiplying negative numbers.

Many students would say that addition is easier because they can "move" the numbers around, where they can't be moved in subtraction.

Pictorial Models for Subtracton:

Solving the same problem using Compensation

Another strategy to solve a subtraction problem  (I think its the Austrian strategy)

Pg. 54 in the Beckman activity manual

Pg. 221 of the Van de Wall book

• examples/strategies that students have used to solve the subtraction problem 73-46, using a number line.
• Add tens to get close, then ones
• Add tens to overshoot, then come back (it's good for kids to know that they can go backwards on a number line)
• Add ones to make a ten, then tens and ones
• Take tens from tens, then subtract ones
• Take away tens, then ones
• Take extra tens, then add back (compensation examples)
• Add to the whole if necessary (compensation examples)

Reading Assignment

• Van de Wall pg. 157 - 161
• Parker 1.5 pgs. 25-30