Lengths and using Mental Benchmarks

Examples, videos, and solutions to help Grade 2 students learn how to develop estimation strategies by applying prior knowledge of length and using mental benchmarks.

Common Core Standards: 2.MD.1, 2.MD.3

New York State Common Core Math Module 2, Grade 2, Lesson 5

NYS Math Module 2 Grade 2 Lesson 5

Lesson 5 Concept Development

Measurements we use to estimate length are called mental benchmarks. The pencil is 20 centimeters. Your pinky is 1 centimeter. The three-ring binder is 30 centimeters. And the length from the doorknob to the floor is 1 meter. You can use these benchmarks at any time by picturing them in your head to estimate the length of an object.

Lesson 5 Homework

1. Name 5 things in your home that you would measure in meters.
Estimate their length.
*Remember the length from a doorknob to the floor is about 1 meter.
2. Choose the best length estimate for each object.
a. Whiteboard - 3 m or 45 cm
b. Banana - 12 cm or 20 cm
c. DVD - 25 cm or 17 cm
d. Pen - 18 cm or 1 m
e. Swimming pool - 50m or 150 cm

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