I had the pleasure of working with a group of 2nd grade students on a chilly Monday morning in December. These students had been studying dinosaurs for several weeks and I was charged with creating a lesson that incorporated their previous studies with mathematical standards. So, I asked the students, “What do you still wonder about dinosaurs?”. It was not surprising when many of their curiosities revolved around the question, “How big were the dinosaurs really?” Thus, a math lesson was born.

We started by reading this great book, *Patrick’s Dinosaurs*. I love this book because it is filled with wonderful illustrations and makes great connections between dinosaurs and mathematical ideas.

Students were then charged to work in small groups to do some research on one of the dinosaurs that appeared in the story. I used these posters to guide the research.

My favorite aspect of this resource is that the units of measure are metric, which was a perfect connection to the base ten work these students had just been engaged in studying.

This research was recorded using the graphic organizer below.

To incorporate the mathematics into this lesson, I told the students that the objective of our math lesson was to compare our length (laying down) to the length of a dinosaur to truly understand the answer to our question “How big is a dinosaur?”. We had a brief discussion about using our tools appropriately. In kindergarten, the CCSS calls for students to align endpoints when measuring and this concept is again reinforced in first grade. I thought it was important to review this key factor of measurement before sending students off to work in groups to measure their height. Then I told them to bundle up and we headed outside!

Students worked collaboratively to measure each others’ length (height) using the meter stick and record their measurements in chalk. Students made observations of who was longer and shorter within their group.

Then students were asked to create a drawing of how long their dinosaur was using the same tool they used to measure themselves. A great challenge in this task was the required iterations of the meter stick to measure the complete length of their dinosaur (many were 9 meters or more!). The final task was to compare their length to that of the dinosaurs they researched.

This group discovered that all their lengths together was still less than the length of the dinosaur they had studied. To quote the young man in purple, “That’s HUGE!!!”

Students were then asked to record the measurements on the back of their research document and determine the difference in their length and that of their dinosaur of study. This proved to be the most challenging portion of the lesson. Here are some examples of student work.

The main math objective of this lesson focused on the following standards:

*2.MD.1 Measure the length of an object by selecting and using appropriate tools such as rulers, yardsticks, meter sticks, and measuring tapes.*

2.MD.4 *Measure to determine how much longer one object is than another, expressing the length difference in terms of a standard length unit *

2.NBT.7 *Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction;*

Students demonstrated proficiency in use of the meter stick both in measuring their own length, as well as in representing the length of a dinosaur using iteration. As you can see in the work samples above, the student on the left misused the standard algorithm for subtraction (not a fluency standard until 4th grade) and calculated the answer incorrectly. I’ve seen this mistake more times than I can count! However, the student on the right used a model (the number line) to solve (which is called out in the standard for subtraction in the second grade), yet still calculated an incorrect answer. It is my determination from this lesson that the class needs more concrete work with subtraction of numbers within 1000, as they are not yet demonstrating proficiency with the representational (number line) or abstract (standard algorithm) solution paths (YET!). I see these mistakes in mathematics as a great opportunity for me as the teacher to determine exactly what the students need to move forward in their understanding of subtraction. After all,

I look forward to pulling out the base ten blocks in future lessons and using these concrete tools to better support these students’ understanding of the base ten system and subtraction.