Mental Math Trick: Multiplying by 11

Matt from Mr J's channel demonstrates a mental math trick for multiplying two-digit numbers by 11. The method involves splitting the number and adding the digits. Examples include 43 times 11, resulting in 473, and 78 times 11, resulting in 858 after carrying over. Viewers are encouraged to try 52 times 11 on their own and share their answers in the comments. A link to a related video on three-digit numbers is provided in the description.

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

• Multiply the digits together

• Divide the number by 2

• Split the number and add the digits

• Subtract the digits

Tags

CCSS.4.NBT.B.5

When using the 'split and add' method, what is the result of 43 times 11?

• 473

• 347

• 734

• 437

Tags

CCSS.4.NBT.B.5

In the example of 78 times 11, what do you do after splitting and adding the digits?

• Subtract the sum from the original number

• Carry over if the sum is greater than 9

• Ignore the sum

• Place the sum directly between the digits

Tags

CCSS.4.NBT.B.5

What is the final answer for 78 times 11 using the mental math trick?

• 785

• 578

• 858

• 875

Tags

CCSS.1.NBT.C.4

CCSS.2.NBT.B.5

What should you do if the sum of the digits is greater than 9 in the 'split and add' method?

• Place the sum as it is

• Ignore the sum

• Carry the tens digit to the next place

• Subtract 10 from the sum

Tags

CCSS.1.NBT.C.4

CCSS.2.NBT.B.5