### Old dog, new math

**Directions for teachers**: After your students read the online *Science News* article “Calculating a dog’s age in human years is harder than you think,” ask them to answer the following questions. A version of the story, “Calculating a dog’s age requires a bit more math,” can be found in the August 15, 2020 issue of *Science News*.

**1. The Science News article expresses two mathematical formulas in words. What are the formulas used to find?**

The formulas are used to find a dog’s age in equivalent human years.

**2. Write the formulas as equations in terms of x and y.**The formulas are y = 7x and y = 16(ln(x)) + 31.

**3. Which formula do scientists claim is better? What evidence do the scientists give to support their claim?**Scientists consider the formula 16(ln(x)) + 31 = y to be more accurate because it is based on a biological comparison between dogs and humans. It takes into account that the relationship between dog and human ages can change over time.

**4.** **Name one limitation of the research presented in the article. What other data would you want to collect to better support the claim?**

The study only looked at Labrador retrievers. That means the formula y = 16(ln(x)) + 31 applies only to Labs. Researchers will have to repeat the study with other breeds to get age conversion formulas for those breeds. Additional data from different dog species should be collected to further support the scientists’ claim.

**5. According to the article, what are methyl groups and what can scientists learn from them?**

Methyl groups are chemical tags that get added and removed from DNA as animals get older. The changes are associated with growth stages. Scientists can compare changes across species and use the changes to track biological age.

**6. Does this article assume any knowledge you may not already have?**Student answers will vary. Students might mention that the article assumes they know the way people typically find a dog’s age in human years is by multiplying the dog’s age by seven.

**7. Who is the author of this article? Did the author perform the research mentioned in the article? Explain.**

Bethany Brookshire is the author of the article. She is a staff writer at *Science News for Students.* Brookshire wrote about the recent dog age research, but she did not perform the research herself.

**8. Name the publication this article is published in. Where is the original research published? Who is the intended audience of each publication?**

This article is published in *Science News*. The research is published in *Cell Systems*. The audience for *Science News* is the general public, and the audience for *Cell Systems* is research scientists.