# Comparing & Measuring Lengths

Comparing and measuring lengths in the first grade is made of two different but related Common Core math standards: 1.MD.A.1 and 1.MD.A.2. Below we show a few videos that demonstrate each of these standards. Then, we provide a breakdown of the specific steps in the videos to help you teach your class.

Prior Learnings

Your students should be familiar with the Measurement and Data standards from Kindergarten. The first grade Comparing and Measuring Lengths standards are a continuation of the Kindergarten skill of describing measurable attributes of objects, like length. And it’s closely tied to the Kindergarten standard of directly comparing two objects with a measurable attribute in common--like identifying which object has “more of” or “less of” an attribute. You may want to give your first graders a quick refresher on these items before jumping into the lesson.

Future Learnings

Measuring and comparing lengths in 1st grade will help your students as they move onto 2nd grade. In 2nd grade, your students will learn how to make determinations on length differences using tools like rulers as well as express those differences in terms of a standard-length unit.

Common Core Standard: 1.MD.A.1 - Order three objects by length; compare the lengths of two objects indirectly by using a third object.

Students who understand this principle can:

1. Identify which of 2 objects is longer or shorter.
2. Place objects in order based on length (longest to shortest or shortest to longest).
3. Decide how the lengths of two objects relate to one another based on a third object’s length.

Video 1: Ordering Objects by Length

This video has 2 parts, both related to 1.MD.A. In the first half 3 objects are ordered by lengths. And the 2nd half, 2 objects are compared using a third object.

1. In the first half of the video, three objects are compared: a pair of scissors, a crayon, and a pen. The video walks you through how to order these 3 objects from shortest to longest. Here’s a breakdown of the specific steps taken in the video:
The three objects are arranged so that they are all straight up and down.
2. A base line is drawn, and the three objects are aligned so that they all begin at the same point.
3. The objects’ heights are compared.The crayon is the shortest, the scissors are the tallest, and the pen is in the middle.
4. Each object is labeled 1-3, with 1 being the shortest (the crayon) and 3 the tallest (the scissors). The objects are sorted from shortest to tallest. Since the crayon is the shortest, the crayon moves to the front of the line, switching places with the scissors. Next, the pen should be second, so it moves to the middle. The order is now shortest to longest: crayon, pen, then scissors.

In the second half, we see how to compare two objects by using the length of another object. Here’s a breakdown of the specific steps taken in the 2nd half of the video:

1. Two flowers are shown, and we want to compare their lengths using another object. In this example, a hand is used to compare the flowers’ lengths.
2. The hand is aligned next to the smaller flower and we see that the flower is about the length of one hand.
3. The same hand is aligned next to the larger flower.
4. The larger flower is the length of two hands. Therefore, the larger flower is about the same as two of the smaller flowers put together.

Video 2: Comparing Lengths

Boddle combines both standards into one video. The first half of the video covers standard 1.MD.A.1 (0:00-1:30), which is broken down below:

This is a helpful video for you to show your students. It introduces how to measure length, following Emma, a Boddle character who is doing some sightseeing in her new neighborhood. Emma asks for students' help in measuring length. Along the way, Emma notices some tall buildings and wonders which is the tallest.

1. The buildings are labeled as A, B, and C, and the viewer is asked to choose among the three to identify the tallest. Building C is identified as the tallest.
2. Next, Emma goes to the ocean and sees three different types of ships. She wants to know which is the longest, and then the viewer gets to choose between the ships labeled as A, B, and C. Ship A is the longest.
3. Then Emma goes to her neighbors house to meet Jamie, Chelsea, and Mike. The viewer is then asked to find which one of the three is the shortest. Chelsea is the shortest.

Common Core Standard: 1.MD.A.2 - Express the length of an object as a whole number of length units by laying multiple copies of a shorter object (the length unit) end to end; understand that the length measurement of an object is the number of same-size length units that span it with no gaps or overlaps.

Students who understand this principle can:

1. Illustrate how to use multiple shorter objects to find the length of a longer object.
2. Connect the length of the longer object to the total number of shorter objects used and express the longer object’s length (e.g. The pencil is 3 paper clips long).
3. Describe why gaps and overlaps are not allowed and do not provide a proper  measurement.

Video 1: Using Paper Clips to Measure Length

The video demonstrates how to measure the length of a pencil using multiple paperclips. At first, the video shows 4 wrong ways to measure the pencil using paperclips.

In the first example, the girl in the video believes her pencil is 4 paperclips long, and then asks the viewer if they can identify what she did wrong. She precedes to present three more attempts at measuring her pencil with paperclips, ending up with varying measurements: 6, 4, and 5 paperclips.

She then lists what she needs to do so that her measurements are accurate. There are 4 things she understands that are needed to ensure accurate measurement using the paperclips:

1. The paperclips should start at the beginning of the pencil and go to the very end.
2. The paperclips need to be placed in a straight line, without overlapping.
3. The paperclips need to be placed end-to-end, without leaving any gaps.
4. The paperclips all need to be the same size.

The girl in the video then measures her pencil once more, making sure all the above criteria are met, and discovers her pencil is 5 paper clips long.

Video 2: Measuring Lengths

The video below covers both standards 1.MD.A.1 and 1.MD.A.2. Below is the breakdown of the 2nd half of the video, which covers 1.MD.A.2 starting at 1:30 on the video.

1. In the first example, Boddle uses cameras to measure the length of a car. The cameras are lined up below the car and counted. The car is about 6 cameras long.
2. Next, houses are used to measure the length of an airplane. The same process is repeated and the viewer finds that the airplane is about 4 houses long.
3. Lastly, dumbbells are used to measure the length of a ladder. The ladder turns out to be about 8 dumbbells long.

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