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: Lily and Ravi are visiting the Redwood Forest in California. They want to measure the height of one of the trees, but they can’t climb it. However, they are able to measure the shadow of the tree. They determine the shadow of the tree is
$$583{1\over3}$$
feet long.
If Ravi is 6 feet tall and they determine his shadow is 10 feet long, find the height of the redwood tree.


aligns: no