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.

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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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