standard_description: Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
problem_activity: Problem 1
Estimate the mass of the following objects in grams or kilograms, depending on which is more appropriate. Then measure their actual mass using your tool(s).
a.   Pair of scissors
b.   Thumbtack
c.   Ruler
d.   Textbook
Problem 2
What is the mass of each of the following objects, according to the reading on the scale? For any measurement that isn’t exact, make your best estimate.
a.
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b.
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c.
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aligns: no