standard_description: Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases:
- The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones.
- The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones).
- 10 can be thought of as a bundle of ten ones — called a “ten.”
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