Mental Math In Subtraction Rounding Base Ten Form Number

Previous Requirement Lessons

• Basic Number Operation Vocabulary 1

• Number Place Value In Mathematics

Example ( Find The Difference Number )

55 - 19 = ...

• Minuend number ( top digit ) in this example is 55.
• Subtraction sign is ( - ).
• Subtrahend number ( lower digit ) in this example is 19.
• Difference number in this example is ( ... )

First Step

Rounding the subtrahend number to the nearest tens of base ten form number. In this example we rounding 19 to 20. Then keep in the mind the additional number is 1.

55 - ( 19 + 1 ) = ...

55 - 20 = ...

Second Step

Subtract the subtrahend number from the minuend number to get difference number. In this example 20 ( subtrahend number ) from 55 ( minuend number ).

55 - 20 = 35

Third Step

Add the difference number by additional number from First Step. In this example add 35 to 1.

55 - 20 = 35 + 1

55 - 20 = 36

Fourth Step

Return the subtrahend number as the number in the question. In this example the subtrahend number return from 20 to 19.

55 - 19 = 36

Bibliography

https://byjus.com/

https://www.ck12.org/

https://www.mathnasium.com/

https://www.splashlearn.com/