Students attempt to calculate their exact age. Because this is a constantly changing quantity, they attend to precision when they think carefully about how accurately to report the answer (MP6). The mathematics involved is multiple unit conversions in the context of time. In addition to the fact that age is always growing, precise times of birth may not be known.
Arrange students into groups of 4. Ask them to order themselves according to their age: who is the youngest? Who is the oldest? What information do you need to know to decide?
Tell students that they will be finding their exact age.
Provide access to calculators. Give students 10 minutes of group work time, followed by whole-class discussion.
What is your exact age at this moment?
Sample response: I was born on April 4, 2011 at 12:09 p.m. Today is December 17, 2024, and right now it is 10:55 a.m. So I am 13 years, 256 days, 22 hours, and 46 minutes old right now. I can’t get any more exact because I don’t know the second I was born. Plus, I’m not sure if I should answer the question for when I begin to write my solution, or for when I will be done writing my solution, because I keep getting older.
Invite students to share answers and discuss difficulties in answering the question. The discussion should include the following points:
Ask students how they usually answer the question, “How old are you?” (This will probably be in whole number of years lived.) Why? (Because this whole number communicates enough information for most purposes.) After more than six months have passed since someone’s last birthday, the person still doesn’t normally round up when they report their age, even though this is customary for reporting many other types of measurements.
If students struggle with what is meant by “at this moment” in the prompt, consider asking:
“Tell me about your age.”
“What does ‘at this moment’ mean to you?”
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Students attempt to calculate their exact age. Because this is a constantly changing quantity, they attend to precision when they think carefully about how accurately to report the answer (MP6). The mathematics involved is multiple unit conversions in the context of time. In addition to the fact that age is always growing, precise times of birth may not be known.
Arrange students into groups of 4. Ask them to order themselves according to their age: who is the youngest? Who is the oldest? What information do you need to know to decide?
Tell students that they will be finding their exact age.
Provide access to calculators. Give students 10 minutes of group work time, followed by whole-class discussion.
What is your exact age at this moment?
Sample response: I was born on April 4, 2011 at 12:09 p.m. Today is December 17, 2024, and right now it is 10:55 a.m. So I am 13 years, 256 days, 22 hours, and 46 minutes old right now. I can’t get any more exact because I don’t know the second I was born. Plus, I’m not sure if I should answer the question for when I begin to write my solution, or for when I will be done writing my solution, because I keep getting older.
Invite students to share answers and discuss difficulties in answering the question. The discussion should include the following points:
Ask students how they usually answer the question, “How old are you?” (This will probably be in whole number of years lived.) Why? (Because this whole number communicates enough information for most purposes.) After more than six months have passed since someone’s last birthday, the person still doesn’t normally round up when they report their age, even though this is customary for reporting many other types of measurements.
If students struggle with what is meant by “at this moment” in the prompt, consider asking:
“Tell me about your age.”
“What does ‘at this moment’ mean to you?”