Mental Math Multiply Two Numbers With Same Tens And Sum Of Ones Is Ten

Previous Requirement Lessons

Basic Number Operation Vocabulary 1

Number Place Value In Mathematics

General Condition:

• Two factor numbers has same tens in number place value.
• Two factor numbers has sum of ones are tens.

Learning Direction

• Student can find the product number more simplified.
• Student get more understand for mathematics concept with practice the following examples.

Method 1 Example

82 × 88 = ...

• Factor numbers in this example are 82 and 88.
• Multiplication sign is ( × ).
• Equal sign is ( = ).
• Product number in this example is ( ... ).

First Step

Split tens with ones for each factor numbers.

82 × 88 = ( 80 + 2 ) × ( 80 + 8 )

Second Step

Multiply ones digit factor (last number) with the other ones digit factor (last number). If the product number in this step only result in ones digit, add zero in the tens number place value.

82 × 88 = ... ( 2 × 8 )

82 × 88 = ... 16

Third Step

Multiply the tens digit factor with the other ten digits factor.

82 × 88 = ( 80 × 80 ) + 16

82 × 88 = 6400 + 16

Fourth Step

Multiply the tens digit with 10.

82 × 88 = 6400 + ( 80 × 10 ) + 16

Result Step

Adding all the result from the previous step with the result in the previous step

82 × 88 = 6400 + 800 + 16

82 × 88 = 7216

Method 2 Example

71 × 79 = ...

• Factor numbers in this example are 71 and 79.
• Multiplication sign is ( × ).
• Equal sign is ( = ).
• Product number in this example is ( ... ).

First Step

Split tens with ones for each factor numbers.

71 × 79 = ( 70 + 1 ) × ( 70 + 9 )

Second Step

Multiply ones digit factor (last number) with the other ones digit factor (last number). If the product number in this step only result in ones digit, add zero in the tens number place value.

71 × 79 = ... ( 1 × 9 )

71 × 79 = ... 9

71 × 79 = ... 09

Third Step

Add result split tens ( from first step ) with 10 number then multiply with result split tens.

71 × 79 = [ ( 70 + 10 ) × 70 ] 09

71 × 79 = [ 80 × 70 ] 09

71 × 79 = 5609

Method 3 Example

56 × 54 = ...

• Factor numbers in this example are 56 and 54.
• Multiplication sign is ( × ).
• Equal sign is ( = ).
• Product number in this example is ( ... ).

First Step

Multiply ones digit factor (last number) with the other ones digit factor (last number). If the product number in this step only result in ones digit, add zero in the tens number place value.

56 × 54 = ... ( 6 × 4 )

56 × 54 = ... 24

Second Step

• Identify the factor number has difference 1 between tens and ones. If there are same identifier between two numbers, choose the biggest one.
• Multiply the ones with ten.

56 × 54 = [ 50 × ( 6  × 10 ) ] + 24

56 × 54 = [ 50 × 60 ] + 24

Third Step

Multiply the tens number with the number from the result.

56 × 54 = [ 50 × 60 ] + 24

56 × 54 = 3000 + 24

56 × 54 = 3024

Bibliography

https://byjus.com/

https://www.ck12.org/

https://www.mathnasium.com/

https://www.splashlearn.com/

https://www.wikihow.com/