Thousands Hundreds Tens Ones Using their Interactive Math Notebooks, the students will write about this action and draw a picture of it. Students will share their IMN entries with each other. Since this is the first time 2nd graders will be ask to draw a thousands block, the teacher may want to give students a quick tutorial: Have students draw 2 overlapping squares as such: Then draw lines to connect the corners. Ask the students what they notice. Do they see a pattern when going from one place to another? Students should be able to explain that if they group ten ones they get a group of ten. If they group ten tens that gives us a group of a hundred. If we group ten hundreds that gives us a thousand. So if we group ten in one place it gives us the value of the next place. That’s how our numbers work; we group ten and move to the next place.
Ordering 3-Digit Numbers The teacher will demonstrate ordering 3-digit numbers. Model solving problem #1 (page 64) using the process as before. Main Idea: list girls’ scores least to greatest Details/Known: M - 322 points L - 223 points S - 232 points The teacher and student table groups build each number from the story problem with base 10 blocks on mats. Have students draw a picture to represent each number beside the corresponding “detail.” Details: M 322 points L 223 points S 232 points As before, students discuss how to arrange the mats from least to greatest. Then they place the mats in order. Ask the students, “How did you decide which number would go first, second, and third?” (Have several students explain their thinking.) This time, demonstrate making a chart which should be used when ordering 3-digit numbers.
Strategy: H T O 3 2 2 2 2 3 2 3 2 First we focus on the hundreds place, since those numbers have the greatest value. What do you see? a 3, and 2 twos Since we are looking for the smallest number, we will disregard the 3 groups of a hundreds for now. But we have two 2 groups of a hundred. So we have to look where? the tens place The first number with a 2 in the hundreds place (2 groups of a hundred) has a 2 in the tens place or 2 groups of ten. The second number with a 2 in the hundreds place has a 3 in the tens place. Which is less, 2 groups of ten or 3 groups of ten? 2 groups of ten So which number is the smallest? (223) Mark it with a 1. Mark the other 2 hundred number with a 2. And what do we mark the 3 hundred number with? (3) Why? (because it is the largest, so it comes last) Write the numbers from least to greatest. 223, 232, 322 How could this relationship be written using < symbols? (223 < 232 < 322) Which number comes between the smallest and the largest number? (232) Have students read inequalities to a partner. As a class, come up with a statement to explain how they got the answer. An example of what the completed 4-step process may look like can be found on the following page.
We also learned that if the numbers both end a 0 we can count by 10s to find the number that is halfway. Let’s count by ten starting with 850 (as students count, ask them to point to where the number would fall on the number line). It may be helpful to write the numbers on the board as students count so they can see the number that is halfway. 850, 860, 870, 880, 890, 900, 910, 920, 930, 940, 950 What number is halfway between 850 and 950? 900 If students don’t know what comes after 890, use base ten blocks to illustrate the regrouping of 10 groups of ten to make a group of a hundred. Let’s place a mark on the halfway point to remind us where 900 is located (you may write the number 900 as well). Now we can draw a line to show were the numbers belong. 3. Partner Practice Partner Practice 2, page 90: Students write 3-digit numbers in their correct location on a number line, then compare their number line with their partner’s. Students should also compare and share their strategies. Remember the focus is on number sense rather than precision. Partner Practice 2 1. Write the numbers 420, 590, and 510 in their correct place on the number line.