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!

If you cannot see the video above, click here for an alternative video player.

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

If you cannot see the video above, click here for an alternative video player.

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