Dog Years
(page 169)

Here's a solution from a group of seventh graders in Easton, Maryland. Their teacher, Maureen Lempke, said,

"I let my students write the response. They typed the short version but explained the process out loud. This is what about what they said:"

We wrote what we knew

Chelsea was born on Dwight's 8th b-day

Chelsea is twice as many dog years old right now as Dwight is in person-years

Dog years is 6

Sadie in person years is 1/3 chelsea age in dog years


Then we knew he had to be middle school age so we drew a table and guessed

Person Years

Dog years








Sadie is 8



Chelsea is 24 dog years
Dwight is 12 people years old
Sadie is 48 dog years old

eeps comments:

This is a nice solution, but points up a problem we all have trying to communicate about math in writing. What does the table mean? Here's what I think:

The first line means that when Dwight is 9, Chelsea will be 1 (person year), therefore 6 dog years. (The C stands for Chelsea). I think the students are tring to see when the clue "Chelsea is twice as many dog years right now as Dwight is in person-years" becomes true. They must be older than this, because Chelsea is still too young.

The second is the next guess, and it's a good one! Three years later, Dwight will be twelve and Chelsea will be 4 (in person years) which is 24 dog years. And that's twice Dwight's age. Whew!

The third line solves for Sadie: her person-years must be 8 (1/3 of 24, last clue), so she's 48 dog years old.

The question is, how could we make that table so it would be clearer without having to write all the sentences I did?

back to the Answer Book page