Units digits: unaffected by higher place values

If you are asked about the units digit of a complicated operation, you can safely ignore the higher place value numbers, as they will not affect it.  The units digit of the product:

2,234,578 \times 98,776,543

is the same as the units digit of the product

8 \times 3

Also, the units digits of powers often repeat, so look for the pattern.  I don’t necessarily recommend that you memorize the patterns, as it takes seconds to find.

(Source: MathCounts)

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