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Level 5: SubWhole

8/13/2015

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When asked to subtract whole numbers, we again must recognize and group together the place values of each number.

Let us try 6457 – 312.  This example does not require any regrouping.  Working from right to left, we have (7 – 2) ones, so we write a 5.

We have (5 – 1) tens, so we write a 4 to the left of the 5.  We have (4 – 3) hundreds, so we write a 1 to the left of the 4.

We have 6 thousands, so we write the 6 on the left.  The answer is 6145.

Let us try an example with regrouping, such as 562 – 275.  We must think of this as (5 – 2 hundreds), plus (6 – 7 tens), plus (2 – 5).

Regrouping, we get (4 – 2) hundreds, plus (16 – 7) tens, plus (2 – 5).  Regrouping again, we get 2 hundreds, plus (15 – 7) tens, plus (12 – 5).

Our answer is 2 hundred, 8 tens, and 7, or 287.

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    I competed in Number sense in the early 1990s.  Now, I'm coaching the next generation of superstars.  Hopefully, this site will be helpful to you.

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