Comparing Number

Spatial Extent Estimator

Sub Trajectory: Numerosity Estimation

Extends sets and number categories to include “small numbers,” which are usually subitized, not estimated, “middle-size numbers” (e.g., 10–20) and “large numbers.” The arrangement of the to-be-estimated set affects the difficulty.

Activities

You may see this:

Other Examples:

Shown 9 objects spread out randomly for 1 second and asked, "How many?," the child guesses, "14."
Shown 25, the child guesses “40."

Help your student become a(n) Spatial Extent Estimator

Activities ask children to estimate the number of objects in a set, with scaffolding that first asks them if it's a small number (e.g., 4 or 6), middle-sized (e.g., in the teens) or large (beyond 20).

The Estimating Jar

Whole Group

Estimate How Many [Spatial Extent]

Small Group