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From Counting to Addition 11<br />

Figure 1-9<br />

When adding three<br />

numbers, it doesn’t<br />

matter which two<br />

are added first. At<br />

A, we add three<br />

and five, and then<br />

add seven more.<br />

At B, we add<br />

seven and five,<br />

and then add three<br />

more. Either way<br />

we get fifteen.<br />

Figure 1-10<br />

Big numbers are<br />

added in the same<br />

way as single-digit<br />

numbers. Here, we<br />

see that 125<br />

added to 324<br />

equals 449.

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