Math Tips

Math Tip #2 : Multiplying by 11 with Regrouping

by | Math Made Easy!, Math Tips | No Comments

If the sum of adjacent digits is 10 or more, the procedure (see Math Tip #1) will have to be modified.
Example: 39 x 11

Step 1: Split the two digits: 3 __ 9

Step 2: Add the two digits, 3 + 9 = 12. The result is a two digit number but only one digit can be placed in between 3 and 9.

3 (12) 9 –> 3 2 9

Step 3: Carry over the 1 from the 12 and add it to the 3 giving a final answer of 429.

(3+1) 2 9 –> 4 2 9

So 39 x 11 = 429.

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