How old can a cat be?
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A cat does not live as long as a human being. So you might say that a cat ages faster than
a human. To compare a cat’s age (number of cat years) with those of a human (number of
years) one might use different models.
Model A: Each year corresponds to 7 cat years.
Model B: The first year corresponds
to 15 cat years.
The second year corresponds
to 10 cat years.
Each additional year
corresponds to 4 cat years.
a)
Three years ago Maria got a newly born kitten. How many cat years old is her cat
today according to Model A and Model B respectively?
b)
Copy and fill in the table.
Cat’s age
Then draw a coordinate system with
Model A
Model B
Year
cat years
cat years
the number of years on the x-axis and
the cat’s age on the y-axis.
1
7
15
Plot two graphs in your coordinate system,
2
14
25
one for Model A and one for Model B.
3
4
5
6
c)
How long does it take until the two models give the same age for a cat? Determine
this as exactly as you can.
d)
Cats can get rather old. It is not unusual that they live more than 20 years. Compare
the two models for the life span of cats (number of cat years). Which of the two
models is most reasonable? Explain and defend your conclusions.
In assessing your work the teacher will take into consideration
• what mathematical knowledge you have shown
• how well you have defended your conclusions
• how well you have presented the solution.
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