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
Read each situation below and then answer the questions that follow.
Situation A:
In the spring, an animal shelter had 216 animals. By the end of the summer, this number decreased by 8%. How many animals were at the shelter at the end of summer?
Situation B:
After advertising for adoptions on local television, an animal shelter decreased the number of animals at the shelter by 8%. There are now 216 animals. How many animals were at the shelter before the advertising?
a.   Sketch a visual diagram to represent each situation.
b.   How are the two situations similar?
c.   How are the two situations different?
Problem 2
A store sells backpacks in two sizes: small and large. The large backpacks sell for 20% more than the smaller backpacks. If a large backpack costs $75, how much does the small size cost?
Draw a visual representation of the situation, and then use an equation to solve.


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