Add and subtract 2-digit numbers without regrouping
In this 1st grade lesson, we add and subtract two-digit numbers WITHOUT regrouping (no carrying nor borrowing). First we do that with a help of a visual model, and then "in boxes", or by writing one number under the other, and then adding/subtracting the ones and the tens.
We also solve several word problems. The first one is challenging, but the visual model (boxes for tens and dots for ones) helps us to solve it easily.
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See also
Add a 2-digit number and a single-digit number mentally - no regrouping — video lesson
Math Mammoth Grade 1 curriculum