Strategies for mental subtraction

These two videos explain various basic strategies we can use to mentally subtract two-digit numbers.

This first part covers two simple mental math strategies for subtracting a single-digit number from a two-digit number, such as 63 − 8 or 72 − 5.

The first strategy is to subtract in parts (or part-by-part). For example, think of 63 − 8 as 63 − 3 − 5. You first subtract 63 − 3 which is 60. Then you subtract the rest.

The second strategy is to use known subtraction facts. To solve 62 − 7 with this strategy means recalling 12 − 7 = 5. Then, the answer to 62 − 7 ends in 5, and is in the "previous ten", or in the fifties, thus it is 55!

A few more mental math strategies for addition and subtraction of two-digit numbers. We also solve a puzzle with two unknowns. :)

See also

Two-digit mental addition — online practice

Mental addition − add a 2-digit and a 1-digit number (with regrouping)

Number rainbow & fact families with 12

Math Mammoth Grade 2 curriculum

Back to 2nd grade videos index

Back to 3rd grade videos index

Back to the index of all videos