SWBAT round to the closest ten or hundred, estimate, and subtract with regrouping to make a pictograph about some water uses that we don't ordinarily think about.

This lesson continues to develop students' understanding of graphing , subttraciton, place value estimation and rounding while giving them an introduction to the myriad of "unseen" water uses.

In this lesson, core third grade math standards are interwoven into science content that builds crucial background that will deepen student understanding of upper-grade NGSS standards, especially for the 5^{th} grade study of Earth’s systems.

**Common Core Math Standards:**

3.NBT.A.1: Use place value and understanding to round numbers to the nearest 10 or 100.

3.NBT.A.2: Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.

**Next Generation Science Standard:**

5-ESS2-2: Describe and graph the amounts and percentages of water and fresh water in various reservoirs to provide evidence about the distribution of water on Earth.

**Cross-cutting Concept:**

**Scale, Proportion, and Quantity:** Standard units are used to measure and describe physical quantities such as weight and volume.

10 minutes

For my lesson opener, I asked students to estimate the amount of water it takes to make a hamburger and a car. Some students immediately said that it takes no water to make a hamburger, which is understandable, but here was an interesting, different response. Though I try to never underestimate my students, I continue to be surprised. Check this out!

An alternative opener would be to do this water use estimation activity created by the United States Geological Survey (USGS).

10 minutes

I demonstrate how to create a pictograph either by hand or in Microsoft Word. I prefer to use MS Word for tables rather than Google docs both because it is easier to manipulate and because it has more options. If you are using MS Word with students, note that it does require extra supervision. In my classroom, the students share laptops, so the MS Word doc needs to be attached to an email, sent to me, and then erased off the desktop immediately.

In my classroom, 1/2 of the students did this on the laptops and the other half did the paper pencil version.

I remind students that the symbol (water droplet) represents a given amount just as a square on a bar graph often represents a quantity greater than one. I believe it's important for students to have constant practice with estimation so they can, over time, develop an understanding of real-world contexts for the variety of quantities we deal with in everyday life. Industrial and agricultural water use in liters is a difficult concept. It's hard to picture the 4,000 - 18,000 gallons of water needed to get to the end product of a hamburger because most of us are very removed from all the steps between birth of the cow and how it ends up on our plate.

35 minutes

In this section of the lesson, students make estimates about water use and then use online sites to compare their estimates to the real data. They then use this information to make a simple pictograph, on which one water drop represents a given amount of water. (This can be determined with the class. I find it works well to use increments of 10 liters).

Students can either use this website or they can use data you provide. The key is to make certain that they make an estimate for each item prior to looking up the actual amount of liters used.

Please keep in mind, these are all averages, and in some cases on the teacher key I have approximated based on information from Water Footprint Network and my own conversions to standard U.S. package sizes.

The Water Footprint site is dense and may confuse students, but one approach to using this site is to have them simply record the amount and not worry at all about the portion size. Remember, the goal is to have them practice creating meaningful graphs from real-world data and also to provide practicing subtraction with regrouping. The content is the vehicle for the skill and they aren't supposed to develop into sudden water use experts!

If you would like to complete this activity offline, here is the Student Page: Liters Used for Food Production & Commercial Uses,

the teacher key, and a pictograph template:

5 minutes

I ask students to respond to one of the following question either verbally or in their journals. I provide question stems for my FEPs and ELLs (official ELL students and those that have been classified as Fluent English Proficient but still have the amazing talents and challenges of all bilingual people).

*How is a pictograph different from a bar graph?**Which do you prefer, a pictograph or a bar graph? Why?**Which is better at communicating an idea, a pictograph or a bar graph? Why? Does it depend on the content?**What is one mathematical and one content area thing you learned in today's lesson?*

This Water Footprint pictograph is a clear, informative example to show the students at the end of the lesson. It can also be shown at the start but I was concerned that some of my students might try to emulate this much more complex format.

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