Name_________________________________________________________
CCSS
F.IF.2
Date __________
Pets
You buy a dog for $400 and you adopt two cats for free. You pay for the cat litter
and food for each animal. Your parents pay for any other costs.
Cat Litter: $10 per month
Cat Food: $15 per month
Dog Food: $20 per month
1. Let x be the number of months. What does c ( x ) = 25 x represent? What
does d ( x) = 20 x + 400 represent?
2. Find and interpret c (3), c (12), d (3), and d (12). Which costs more after
1 year?
3. In the first 4 years, your parents paid $1850 in veterinary bills and other
costs. Did you pay more altogether or did your parents? Explain how you
found your answer.
4. Solve c ( x ) = d ( x ). Explain the result.
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Big Ideas Math
Performance Tasks
3
CCSS
F.IF.2
F.IF.2
Common Core State Standard
Use function notation, evaluate functions for inputs in their domains,
and interpret statements that use function notation in terms of a context.
CCSS
F.IF.2
Grading Rubric
Answers
Score
1. your total cost (in dollars) for the cats after x months;
2
your total cost (in dollars) for the dog after x months
2. $75, cost for cats after 3 months; $300, cost for cats after 1 year;
$460, cost for dog after 3 months; $640, cost for dog after 1 year;
The dog costs more after 1 year.
3. You paid more; Substitute x = 48 in each function to get a total
5
2
cost of $1200 + $1360 = $2560, which is greater than $1850.
4. x = 80; You will have paid the same amount for the cats and the
dog after 80 months, or 6 years and 8 months. Before that, the dog
costs more and after that, the cats cost more.
2
Precision
1. Student relates the values in the functions to the information given
in the problem statement.
2. Student understands to substitute the number in the parentheses in
the given function.
3. Student finds the total cost for the pets and compares it to the
parents’ cost.
4. Student sets the equations equal and solves for x.
Total Points
4
Big Ideas Math
Performance Tasks
1
1
2
1
16
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All rights reserved.