Casting Out Elevens is a slightly slower but more accurate way to sanity check your work. It is a great way to catch most errors including digit reversals (transposing two digits).
Casting Out Elevens can be used when multiplying numbers of any size.
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Find the digit sum for each number being multiplied.
Multiply each digit sum together.
Find the digit sum for the multiplication problems answer.
The multiplication problems answer is probably correct if the digit sums found in Step 3 and Step 4 are the same.
8 = 8 so 156648 is probably correct.