The purpose of this Estimation Exploration is for students to practice the skill of estimating a reasonable length based on their experience and known information. They are given an illustration of a boy and a fish and are asked to give an estimate for the length of the fish in inches. This gives students an opportunity to share a mathematical claim including the assumptions they made when interpreting the image with limited information (MP3, MP4). After students are given more information, they have an opportunity to revise their estimates.

This is the first time students experience the Estimation Exploration routine in grade 2. Students are familiar with this routine from a previous grade, however, they may benefit from a brief review of the steps involved.

• “How did you revise your estimate when you found out how old the boy was and his height?” (My first estimate was a lot higher, but it looks like if this fish was touching the ground too, they'd be closer to the same length. The fish looks about 20 inches higher or longer, but it isn’t touching the ground. I added 12 more inches, which is 60.)
• If it doesn’t come up, point out that the fish is not touching the ground.

The purpose of this activity is to introduce the foot as a U.S. unit of length. Students learn that a foot is longer than an inch and is the same length as 12 inches. They use the length of 12-inch rulers as a tool to measure lengths in feet by iterating the length of a ruler. Iterating lengths of a ruler to measure in feet helps students build a mental benchmark for the approximate length of a foot that they can use to estimate lengths.

Students measure lengths of tape that represent realistic lengths of different types of fish. They measure each length to the nearest inch and to the nearest foot. In the Activity Synthesis, students discuss the difference in their measurements and relate the differences to the size of the length units (MP7).

The purpose of this activity is for students to make decisions about the length units and tools they use when measuring the lengths of objects (MP5). Monitor for the reasons students give for choosing their length unit or tool based on the length of the object they are measuring. When measuring items that are not a whole number of feet long, encourage students to consider using feet and inches to build their understanding that the length units are part of the same system of measurement.

In addition to inch tiles and rulers, it is recommended that students use a retractable measuring tape (tape measure) that marks the length of each foot. If measuring tapes are not available, students may use yardsticks or other tools that are longer than 12-inches. Keep in mind that if your “yardstick” is the same as your meter stick, it is longer than 36 inches and may not indicate the length of each foot. If these tools do not mark the length of each foot, take the time before measuring to show students how to use a ruler to check the length of each foot. If possible, label the length of each foot on the tool before students begin measuring.