Lesson 1 Compare, Count on, and Count Back

    • Let’s compare numbers and add or subtract.

Warm-up Number Talk: Count Back

Find the value of each expression mentally.

Activity 1 Notice the Difference

Problem 1

Students playing card game.

Tyler and Elena were asked to find the value of .
Their work is shown.

Tyler

Base ten diagram. 7 tens, crossed out. 11 ones, 9 crossed out.   

Elena

Number line. Scale 75 to 85. 11 evenly spaced tick marks. First tick mark, 75. Sixth tick mark, 80. Eleventh tick mark, 85. Arrow from a point at the fifth tick mark to 80, and arrow from 80 to a point at the seventh tick mark.

What do you notice? What do you wonder?

Problem 2

  1. Locate and label 203 and 198 on the number line.

    Number line. Scale 180 to 210 by fives. Evenly spaced tick marks. First tick mark, 180. Last tick mark, 210.

  2. Compare using >, <, or =.

  3. Find the value of . Show your thinking.

Problem 3

  1. Locate and label 673 and 680 on the number line.

    Number line. Scale 660 to 690 by fives. Evenly spaced tick marks. First tick mark, 660. Last tick mark, 690.

  2. Compare using >, <, or =.

  3. Find the value of . Show your thinking.

Problem 4

  1. Locate and label 501 and 499 on the number line.

    Number line. Scale 480 to 510 by fives. Evenly spaced tick marks. First tick mark, 480. Last tick mark, 510.

  2. Find the value of . Show your thinking.

Problem 5

Find the value of . Show your thinking.

Activity 2 What’s the Big Difference?

Number line. Five tick marks. Arrows from 234 to 334, from 334 to 434, from 434 to question mark, from question mark to question mark.

Problem 1

  1. Fill in the missing numbers.

    Number line. 5 evenly spaced tick marks labeled 502, blank, 702, blank, and 902.

  2. Does this number line show counting on by 10 or counting on by 100?

Problem 2

  1. Fill in the missing numbers.

    Number line with 5 evenly spaced tick marks. First two tick marks labeled blank. Next 3 tick marks labeled 332, 342, and 352.

  2. Does this number line show counting on by 10 or counting on by 100?

Problem 3

  1. Fill in the missing numbers.

    Number line. 5 evenly spaced tick marks labeled 278, blank, 478, 578, blank.

  2. Does this number line show counting on by 10 or counting on by 100?

Problem 4

  1. Fill in the missing numbers to show counting on by 10.

    739, 749, , 769,

  2. Explain how you can tell your numbers show counting on by 10 and not counting on by 100.

Practice Problem

Problem 1

Find the value of each difference. Show your thinking.