Addition and Subtraction Algorithms

Making Exchanges

Chip Abacus HundredsTensOnes Making Exchanges

Place-Value Representation ThousandsHundredsTensOnes Making Exchanges

Standard Addition Algorithm Right to left (But left to right is better). WE use a word, “carrying,” that does not explain what students are doing. Countries where the vocabulary for numbers and operations is more descriptive have students who do ________ at math.

Lattice Addition “lines up” Powers of Ten

Scratch Addition

44 – 27 with base 10 pieces Making Exchanges

85 – 68 with Chip Abacus

447 – 375 Making Exchanges ThousandsHundredsTensOnes

447 – 375 Subtracting from the Base – (10 – 6) + 4 versus (10 + 4)

447 – 375 Subtracting from the Base –

Adding the Compliment What my mother learned! 743 – 567 = (433 – 1000) = ( ) – 1000 = 1176 – 1000 = …. = 176 Just a bit different from your book, but really the same thing.

A Few Favorite Algorithms Cashiers subtraction B11 Equal additions B12

Base 5 Anyone?

And in every base! Base n pieces Chip abacus Place-Value Boards