Mental Math Trick: Multiplying by 11

In this video, Mr. J introduces a mental math trick for multiplying three-digit numbers by 11. The method involves splitting the end digits and adding them to find the middle digit. The video provides examples with 245 and 439, demonstrating the process step-by-step, including handling carry-over digits. Viewers are encouraged to try the method themselves with the number 526 and share their answers in the comments.

What is the first step in the mental math trick for multiplying a three-digit number by 11?

• Split the end digits

• Multiply the number by 10

• Subtract 1 from the number

• Add all the digits together

Tags

CCSS.2.NBT.B.7

When using the 'split and add' method on 245, what is the sum of the end digits?

• 9

• 6

• 7

• 8

Tags

CCSS.4.NBT.B.5

In the example of 439 times 11, what do you do after splitting the end digits and adding them?

• Multiply the sum by 2

• Subtract the sum from the middle digit

• Place the sum in between the end digits

• Ignore the middle digit

Tags

CCSS.5.NBT.B.5

What is the final answer when multiplying 439 by 11 using the mental math trick?

• 4629

• 4929

• 4829

• 4729

Tags

CCSS.1.NBT.C.4

CCSS.2.NBT.B.5

How do you handle a double-digit sum when using the 'split and add' method?

• Subtract the extra digit from the total

• Carry the extra digit over

• Add the extra digit to the next sum

• Ignore the extra digit

Tags

CCSS.1.NBT.C.4

CCSS.2.NBT.B.5