Students fill in missing numbers on 10x10 number grids and complete number sequences up to 100, practicing ordering and spacing of whole numbers. A number line from 0 to 20 is shown and students are asked to use it to write numbers that are missing when counting by 5s from 1. Activities ask students to count by 2s, 3s, 5s, 10s and to place numbers before and after randomly drawn cards from 1–100, reinforcing number placement along a linear scale.

Students represent whole numbers as lengths from 0 by "jumping" on a number line (Activity 1) when they start at 0 and move up spaces to reach 9, drawing humps between successive numbers. Students use a laminated number line and complete the "Adding on a Number Line" sheet (0–20) to model addition by starting at zero or at the first addend and counting forward by the second addend (examples include 6+10, 8+12). The included number line images show equally spaced integer marks and arcs that illustrate adding by successive unit jumps.

Activity 2 asks students to use a number line to solve 6 - 3 = ? and instructs using a laminated number line to start at the bigger number and count back the steps. The Student Activity Page middle section directs students to solve 18 - 6, 12 - 4, and 15 - 9 using the number lines provided. Several subtraction activities (e.g., Bowling for Differences, Writing Subtraction Number Sentences) require students to find differences within 100, some using concrete or visual tools including number lines.

The lesson explicitly asks students to use a number line as one of several strategies to find differences (Activity 1 suggests "fingers, drawing, counters, number line"). Students are prompted to write subtraction number sentences for word problems (Activities 1 and 3) and to create and solve subtraction word problems based on given number sentences (Day 2). The Skills section also directs students to represent problems using drawings and equations with a symbol for the unknown.

Students practice whole-number addition and subtraction in multiple activities: the "Fact Power 2" timed sheet and flashcard rounds require finding sums and differences (many problems involve numbers up to and above 20). In the "A Day at the Fair" tasks students add and subtract ticket costs to solve one- and two-step word problems and reason about remaining tickets. Activity 2 has students enter and compute addition and subtraction sentences on a calculator and keep score, reinforcing computation of sums and differences.

Students use number lines labeled from 0 to 10 and from 0 to 20 to find differences (Counting Back example 10 - 4 = 6 and the USING SUBTRACTION STRATEGIES page). The Counting Up example (12 - 8 = 4) has students start at the smaller number and count forward on a number line to represent the difference. Multiple two-digit subtraction problems within 100 are practiced with explicit direction to use the number line as a visual aid.

Students create addition sentences from number cards (1–50) and write and solve them, practicing adding two whole numbers. Students compute whole-number differences within 100 (examples given: 39–26, 15–4, 48–44) as part of the wrap-up. Students represent whole numbers using base-ten blocks and place-value cards (showing hundreds, tens, and ones) for numbers up to 1000.

Students are asked to find 0 on a ruler and to line objects up at 0 before measuring, showing whole numbers as lengths from 0 on a ruled number scale. Students measure straws in whole inches and the teacher draws a 5-inch line and asks how its length changes when an inch is added or removed, demonstrating lengths as positions along an equally spaced inch scale. Students complete number grids (1–100 and 101–200) and practice counting by tens while pointing to numbers, reinforcing ordered number positions.

Students measure objects by lining an edge at the 0 mark on a ruler and read off centimeter values (Activity 1 and Activity 3). Students use a meter stick with marked centimeters and are asked to identify the 100-centimeter mark and compare lengths (Activity 3). The lesson also gives whole-number addition and subtraction problems within 100 for students to compute (Wrapping Up).

Students use rulers and a meter stick to measure body parts in inches and centimeters and are asked to show specific unit marks (inch, foot, centimeter, meter) on those tools. Students complete 10x10 number grids (e.g., 401–500) and lay multiple grids in order to count by hundreds and point to specific numbers. Students locate numbers that are 1 more, 1 less, 10 more, and 10 less (e.g., 455, 397, 209, 299) and identify odd and even numbers using the number grids.

The Plotting Heights activity gives students a number line from 39 to 49 with equally spaced inch marks and asks them to plot each child's whole-number height as points on the line. The Measurement Problems require students to write number sentences and compute whole-number sums and differences (for example, 3+6, 11-5, 12-9, 29-26) within 100. Day 2 measurement tasks have students measure physical lengths with rulers and meter sticks and identify objects that are 1, 2, 3, or 4 units long.

Students measure line segments to the nearest whole centimeter and record those whole-number lengths on a horizontal axis marked with the numbers 1 through 6. The Student Activity Page asks students to place Xs on the line plot above the corresponding whole-number measurements, and instructions tell students to space labels evenly and treat the plot like a number line. Activity 2 also asks students to create a line plot by spacing labels evenly and placing marks corresponding to measured quantities.