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: Rishi is trying to find the total number of clouds in the following array.
[IMG]
Rishi says "I know 3 × 9 = 27, so I can use that to help me solve."
a.   Mark the array above to show how Rishi is thinking about it.
b.   Use the fact that
$$3\times9=27$$
to find the total number of clouds in the array.


aligns: no