Students in 1st and 2nd grade work to learn about measuring length to the nearest whole unit.
They learn to use measurement tools that measure in repeated units that are equal in length, laid out like a number line on rulers, tape measures, and yard or meter stick.
Students are also introduced to the most common metric and customary measurement units: centimeters, meters, inches, feet, and yards.
3rd graders further develop their understanding of measurement by incorporating their growing knowledge of fractions and use of the four operations to solve problems involving measurement units.
MA.3.M.1.1 – Select and use appropriate tools to measure the length of an object to the nearest centimeter, half inch, and quarter inch.
Estimating Length
As children progress through elementary school, they develop more refined skills to estimate length, height, and distance.
This process begins by understanding the relative size of measurement units. There are about two-and-a-half centimeters in an inch, and a quarter is about an inch wide. Tiny objects can be measured in centimeters or fractions of an inch. Feet are shorter than yards and meters, and meters are a little longer than yards.
The ability to estimate the length of objects in appropriate measurement units helps students make mental comparisons and understand the magnitude of measurements they may encounter on a regular basis.
Measuring to the Nearest Centimeter in 3rd Grade
Since centimeters are very small measurement units, students will measure to the nearest whole unit.
“Using appropriate tools” means children use measuring devices best suited for the length of an object. Measuring the length of a classroom with a ruler in centimeters would be time consuming and not very accurate. Students develop this understanding given plenty of opportunities to measure a variety of objects in different units.
Measuring small objects with rulers in centimeters is detail-oriented work. Items to be measured need to be aligned with the zero on the measuring tool, which builds their understanding of the number line. The length of the object is determined by the whole centimeter closest to its end.
Measuring Length to the Nearest Half & Quarter Inch
3rd graders use their new understanding of fractions on a number line to measure appropriate items to the nearest half and quarter inch.
Since inches are longer than centimeters, there is enough space between whole inches to determine the best choice for the measurement.
1/4 inch will be closer to the lower whole inch. 3/4 inch is closer to the higher whole inch. 1/2 inch is equidistant between the two inches, much like the endpoints for rounding.
Students in 3rd grade should practice measuring in fractions of inches to build an understanding of benchmarks – items that are “about” 2 inches long, or objects that are “a little more than” 6 inches long.
Standards
Florida’s B.E.S.T. Standards are very specific about the measurement skills that need to be developed in 3rd grade. Since understanding measurement is an important life skill and important mathematically, this level of clarity is appreciated.
The Common Core Standards don’t have a dedicated standard for measuring length but do mention “generating fraction measurements” to build a line plot.
TEKs addresses representing fractions of halves, fourths, and eighths on a number line and relating it to measurement using rulers. TEKs does not specify that 3rd graders will practice this skill by measuring objects with rulers.
Students learning following the BEST trajectory will have the most well-grounded experience with measurement, better preparing them for adding on to these skills in the 4th grade.
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