Multiplying by 11 Trick

Multiplying by 11: Extending the Sequence

I am learning to use what I know about properties of multiplication and place value to multiply numbers by 11.

Success Criteria

I can use the distributive property to multiply numbers within 15 by 11.

Yesterday we learned

How does it work?

Mary’s older brother taught her a “trick” to multiply two-digit numbers by 11. He said,

“When multiplying any two-digit number by 11, just add the two single digits together to identify the middle number. For example,

Multiple Select

Will adding the two single digits together to identify the middle number work for...

• 11 x 13

• 11 x 14

• 11 x 15

Yes, this works for 11x13

Yes, this works for 11x14

Yes this works for 11x15

Fill in the Blanks

What is 11x19?

The 11x Trick

• An understanding of place value and the standard algorithm for multiplication explain why the x11 “trick” works when multiplying a two-digit number by 11.

• An understanding of place value and the standard algorithm can also explain the 10 groups and 1 more group method.

• Remember, For a fact like 11 × 7, think 10 × 7 = 70, then add another group of 7 to make 77.

• For a fact like 11 x 15, think 10 x 15 = 150, then add another group of 15 (150 + 15) to make 165.

FOR THE NEXT FEW SLIDES, JUST WRITE THE ANSWER

DO NOT WRITE AN EQUATION, JUST THE ANSWER!

Fill in the Blanks

11 x 18 =

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11 x 15 =

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11 x 17 =

Fill in the Blanks

11 x 16 =