Mental math: Add and subtract multiples of 100

In this math lesson for 2nd grade, I show how easy it is to add and subtract whole hundreds (numbers such as 200, 500, 600, etc.) to any other 3-digit number. It really is so easy that Mathy, my mascot, at one point asks for a more difficult problem - so I provide one for him. :)

Of course, adding and subtracting multiples of 100 mentally is based on place value... we only need to "worry about" the hundreds digit changing in the result.

See also

Add and subtract multiples of ten from 3-digit numbers (mental math)

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

Math Mammoth Grade 2 curriculum

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