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Everyday MathematicsTrade-First Subtraction

Trade-First SubtractionAs the name suggests, trade-first subtraction involvesmaking all place-value trades first. This makes trade-first easier because we dont have toswitch back and forth between subtracting and trading.Everyday Mathematics

Trade-First SubtractionEveryday MathematicsSolve: 471 293

We set up the problem bywriting the numbers in theirplace-value columns.H= hundredsT = tensO= ones

H

471 293

T

O

Trade-First SubtractionEveryday MathematicsSolve: 471 293HTO611471 293

First we must decide wheretrades need to be made. Thetrades can be made in any order.Here we start with the onesplace.

Because 1 minus 3 results in anegative number, we trade 1 tenfor 10 ones.

Trade-First SubtractionHTO31611471 293

Everyday MathematicsSolve: 471 293Next we look at the tens place. Because 6 minus 9 results in anegative number, we trade 1hundred for 10 tens.

Trade-First SubtractionHTO31611471 293178

Everyday MathematicsSolve: 471 293Now that all trades have beenmade, we can subtract in anyplace-value order.471 293 = 178

Trade-First SubtractionWhen children use trade-first subtraction they practice avariety of skills related to number sense and algebraicreasoning. For example:Writing numbers using place value;Breaking a hundred into 10 [10s] and breaking a ten into 10 [1s]; andRenaming numbers after shifting a group of 10 [10s]or 10 [1s] to the place-value column to the right.

Everyday Mathematics