Mental math: add and subtract multiples of ten
In this mental math lesson, we look at adding and subtracting multiples of ten (20, 30, 40, 50, etc.) to/from a 3-digit number mentally. It is very easy!
First, we do a few of these addition and subtraction problems with the help of a visual model - to show clearly that it is based on place value: we simply add the tens to the existing tens.
Then we solve some more challenging problems, a word problem involving Mathy, my mammoth mascot, and lastly we look at a number pattern of sorts.
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See also
Mental addition - add a 2-digit and a 1-digit number (with regrouping)
Number rainbow & fact families with 12
Math Mammoth Grade 2 curriculum