standard_description: Fluently add and subtract within 20 using mental strategies. (See standard 1.OA.6 for a list of mental strategies.) By end of Grade 2, know from memory all sums of two one-digit numbers.
problem_activity: Problem 6
Pre-unit
Find the value of each expression.
\(206 + 543\)
\(327 + 181\)
\(674 - 129\)


aligns: no