Students are given number-bond tasks where an adult places objects in the whole (large) circle and in one part (small) circle and asks the student to determine the missing number in the other part (for example: large = 4, one part = 1, student finds the other part = 3). Students use manipulatives (pennies, base-10 unit blocks) and the number-bond diagram to represent part-part-whole relationships and to find the unknown part. The materials explicitly note that this activity serves as a simple introduction to subtraction.

Students are asked to determine "How many more?" in Activity 5 (Kate has 5 cookies, Thomas has 3) and to model the problem with counters, base-10 blocks, or an abacus, counting how many more beads appear on the larger group. Activity 6 requires students to record two rolled numbers and complete the sentence "_____ is _____ more than _____," and allows students to use a number line, counters, cubes, or an abacus to determine how much more one number is than another. Activity 2 has students show that one number is "one more than" another by building groups with unit blocks, which practices the add-one/compare concept.

Students use the abacus and the Number Chant (e.g., "6 is 5 and 1", "7 is 5 and 2") to show how a number is made by combining 5 with another number. Students complete the "Combining With 5" activity page where they draw or move beads to add more beads to reach target totals (rods labeled 10, 9, 8, 7). Activities ask students to say phrases like "2 combines with 5 to make 7," and to physically add the missing beads to make the total.

Students practice finding the missing addend to make 10 in Activity 7 ("What's Missing?") where equations like 10 = 6 + ( ) appear and students must supply the missing number. Activity 5 (Number Bonds) and Activity 6 (Ten Chains) have students create and manipulate part–part–whole representations and ask questions like "What combines with 2 to make 10?" The Wrapping Up exercise asks students to call out the number that combines with a given number to make 10, reinforcing finding the unknown addend. Activity 8 (Fish Stories) has students model situations where fish join or leave, allowing practice with join and take-away scenarios that relate to unknown-addend thinking.

Students are given the cookie problem (need 10 cookies, have 5 — how many more?) which asks them to find the number that must be added to 5 to make 10. The skills and activities ask students to decompose numbers 11–20 into 10 and other ones and to show 11 on the abacus by placing 10 beads then 1 more, then count beads to confirm. Coin tasks ask students to make amounts in multiple ways (for example, show 7 cents as 7 pennies or as 1 nickel + 2 pennies), which requires finding the additional coins needed to reach a total.

Students practice number bonds with 10 in the large circle and name pairs that make 10 (e.g., 1 and 9, 2 and 8). In Activity 3 students draw numbers 11–20, place the drawn number as the total in the large circle, and use the abacus to find and write the other addend when 10 is in one small circle (e.g., 15 → 10 and 5). The lesson also reinforces complements to 10 through chants and manipulatives.

Students create and use "number bonds" cards that ask questions such as "Which number bonds with 5 to make 10?" and "Which number bonds with 10 to make ___?" Students sort cards into a number-bonds group, fill in blanks on partially completed cards, and make blank number-bond cards with their own numbers. The activities require students to find the missing addend that combines with a given number to make a target total (within 1–20).

In Activity 1, a child has 3 pretzels and the adult has 2; the child is asked how to make the counts equal and gives another pretzel, demonstrating finding the addend needed to make amounts equal. The child is also asked to place any number fewer than 10 on her plate and then determine how many pretzels the adult should put on theirs so the plates are equal, counting out that number. The activity directs the child to write a number sentence (e.g., 6 = 6) after making the amounts equal, linking the concrete action to an equation.

Students use number bonds and an abacus in Activity 5 to place 10 in the large circle, place a given addend (for example 1 or 2) in one small circle, and find the other addend (for example 9 or 8) that makes 10. Students complete a table showing all pairs that add to 10 and read the pairs as number sentences ("one plus nine equals ten," etc.). Students make wristbands that must total 10 and then write the two addends as number sentences, and Animal Addition pages include blanks such as "_ + 2 = _" and "_ + _ = 7" for students to fill in missing addends.

Activity 2 "What's Missing?" has students create two piles of counters, count up to a target (10 or 8), and write the equation 4 + ? = 10; students also solve explicit unknown-addend equations shown on the whiteboard (5 + ? = 7, ? + 3 = 5, 2 + ? = 8). The Skills list explicitly states "Understand subtraction as an unknown addend problem," and students use counters, drawings, the abacus, and number sentences to find the missing addend. Day 2 narration and questions model number sentences such as "12 minus 5 equals 7," linking subtraction situations to equivalent addition representations.

Students act as the clerk in Activity 2 (How Much Change?) where they use a play ten dollar bill and ten one-dollar bills to give correct change. The example has students buy items totaling $4 and then give back $6, explicitly asking them to determine how much must be added to the purchase amount to make $10. Students switch roles and catch/correct intentional mistakes, reinforcing the idea of finding the missing amount that combines with the purchase to equal ten.

Students are asked explicit difference questions such as "How many more spotted fish than striped fish are there?" and "How many more seahorses than sharks are there?" The lesson directs students to find differences by counting squares in bar graph bars (for example, noting there are two more orange Skittles than green ones by counting extra squares). Students create and read bar graphs and answer questions that require finding how many more of one category than another.

Students are asked to use subtraction to find differences in Activity 2, with prompts such as determining who has more or fewer counters and lining up counters to compare amounts. Students solve word problems that state relational information (e.g., "Marta has 2 more than Beth," "Jack has 3 fewer than Beth," "Chase has 4 fewer than Marta") that require computing unknown quantities. The activity directions tell students that they will either add or subtract to answer the questions and then record the resulting numbers in a table or graph.

Students solve contextual subtraction-to-target problems (for example, the walking problem: total goal 10 miles, current total 8, ask how many more are needed). The Something's Missing activity has students find unknown addends in equations such as 5 + ___ = 10 and 4 + ___ = 8 and also solve a subtraction with a missing minuend (___ - 3 = 1). The materials allow students to use counters, an abacus, and a number line and ask students to write number sentences and read them aloud, supporting work with missing numbers.

Students roll one die and name the number that combines with the rolled number to make 10 (for example, roll a 3 and say "seven"). Students use 10 counters and an abacus to create groups that add to 10 and write addition sentences (e.g., 3 + 3 + 4 = 10), and they record complements to 10 on the "Making 10 with Three" sheet. The activities repeatedly require students to find the missing addend that makes a total of 10.

Students are asked explicitly to find complements to 10 (e.g., "What number adds to 8 to make 10?" and "What adds to 7 to make 10?"). Students model these problems on the abacus and with counters by trading beads or moving groups to make 10, and they complete the "Making 10 to Add" problems (e.g., 8+5, 6+8, 7+5). The "What 5 Makes" activity has students fill in missing addends (e.g., 5 + __ = 7; __ + 5 = 10), reinforcing finding a missing addend.

The lesson's Skills list explicitly states that students will "Determine the unknown whole number in an addition or subtraction equation relating three whole numbers." Activity 3 (Filling the Boxes) has students cut out numbers and place them in boxes to "answer the given subtraction sentences correctly," a self-checking task that requires selecting the number that completes a subtraction equation. Several activities encourage forming subtraction sentences (e.g., egg carton, domino war, card draws) and checking answers with manipulatives.

The Skills list explicitly includes "Determine the unknown whole number in an addition or subtraction equation relating three whole numbers." In Activity 1 Question 5 students are asked, "The zookeeper wants to have 10 elephants at the zoo. How many more does he need?", which requires finding the number that must be added to the current count to make 10. Students are asked to create number sentences for each problem and to identify addition versus subtraction, and they may use manipulatives (abacus/counters) to find the missing amount.

Students are asked explicitly, "What number combines with 10 to make the missing number?" and given the example: for missing number 11, they answer 1, showing they find an addend that makes the total. Students create subtraction sentences that begin with the target number (e.g., 12 − 1 = 11) and are required to produce two subtraction sentences with the missing number as the first number on the Missing Number Sign Requirements sheet. Students use counters and an abacus to partition and find groups that add to the target number, supporting finding unknown addends.

Students complete timed math fact practice and a "Math Facts Quiz 1" that includes subtraction problems (4 - 0, 3 - 3, 5 - 4, 3 - 1, 3 - 2). The introduction instructs students to use addition and subtraction knowledge (turn-around facts, the role of zero, adding/subtracting 1) when solving facts. The Skills list states students will "Add and subtract within 20, demonstrating fluency for addition and subtraction within 10," indicating practice with subtraction facts.

Students practice subtraction facts to 10 through timed flashcards and drills (Introduction: subtraction flashcards to 10). Students play a subtraction-fact game (Minus Mission) and complete a Math Facts Quiz that includes subtraction problems (6-2, 8-7, 8-4), supporting fluency with basic subtraction. The lesson's skills list explicitly includes adding and subtracting within 20 and demonstrating fluency within 10, which frames subtraction practice.

Students practice subtraction within 10 through Activity 2, which directs them to play a mixed addition-and-subtraction facts game and then complete the 'Math Facts Quiz 5' worksheet that includes problems such as 10 - 8, 10 - 5, 8 - 1, and 6 - 6. The materials explicitly ask students to note whether a problem is asking them to add or subtract and remind them of strategies including "adding to 5 and 10." Students also repeatedly solve subtraction problems during timed practice, providing repeated exposure to subtraction facts.

In Activity 3 students are asked, "How many more do you need to get to 100?" and are guided to determine how many additional groups of 10 are needed (for example, if she has 4 baggies of objects, how many more will she need to get to 10? (6)). The teacher prompts students to count remaining baggies or plates to determine how many more groups are needed and to count by tens to show they reached 100. The lesson repeatedly frames missing quantity questions (How many do you have now? How many more do you need?) that require finding an addend that completes a target total.

Students are given number-bond tasks that ask them to find the number that, when added to a given number, makes 10 (Activity 2: 10 in the large circle and 3 in a small circle; student finds 7 and writes 3+7=10). Students use the abacus to find how many tens to add to 30 to make 100 and write 30+70=100 (Activity 2), and they complete a 'Making 100' worksheet with problems of the form X + ___ = 100 (Activity 3). Students read and say the resulting number sentences aloud and model the missing-addend reasoning with manipulatives (abacus, ten rods, base-10 blocks).

Students write and solve subtraction sentences with multiples of ten (e.g., 40-20=) and use base-10 blocks or an abacus to model taking away tens in Activity 3. The materials include several subtraction problems (60-30, 80-20, 90-50, 100-30) on the student matching page and ask students to remove ten rods or move beads to find the difference. The text explicitly reminds students that subtraction is the opposite of addition and connects subtraction practice to prior work adding multiples of ten.

Students complete a "Today's Number" routine that asks them to write the number and to create an addition or subtraction sentence to show the number. Students fill a table labeled "1 more / 1 less / 10 more / 10 less," explicitly computing values that require subtracting 1 or 10 (for example, writing that one less than 26 is 25). The activity pages also ask students to represent numbers with base-10 blocks and place-value charts, which supports reasoning about parts of a whole.

The lesson's Skills list explicitly includes "Determine the unknown whole number in an addition or subtraction equation relating three whole numbers," which names the idea of finding a missing number in equations. Students practice subtraction when they "find the difference between the numbers" with number cards and when they judge subtraction sentences as true/false (e.g., 5-1=2, 9-6=3). Students also work with the meaning of the equal sign and are asked to change false equations to make them true, which engages reasoning about equivalent sums and differences.

Students complete a "Multiples of 10 Number Bonds" activity in which they fill two smaller circles with multiples of 10 that add to a given total (e.g., 60 → 20 and 40). Students also practice subtraction of multiples of 10 (e.g., 60 - 40) using an abacus and base-10 blocks, showing minuends and physically removing tens to find differences. The wrapping-up activity has students draw two multiples-of-10 cards and either add or subtract them, encouraging mental strategies or use of manipulatives.

Students write both addition and subtraction number sentences from pairs of multiples of ten (Activity 1) and compute the sums and differences (e.g., 30 + 60 = 90; 60 - 30 = 30). Students use base-10 blocks and an abacus to model sums and differences of multiples of ten and are reminded to start with the larger number when subtracting. Activity 2 gives explicit subtraction problems (for example, 60 - 50, 80 - 20, 100 - 10) and asks students to decide whether each sentence requires adding or subtracting and to think of multiples of ten as numbers of tens.

Students are asked to solve a 'how many more' problem on the "Multiples of 10 Problem Solving" page (e.g., "How many more coins need to be added to make 40 coins if there are 20 coins initially?"), which requires finding the addend that, when added to 20, makes 40. The Getting Started questions mention subtracting and using place-value patterns to add and subtract, indicating subtraction is at least conceptually considered. The wrapping up and other activities repeatedly ask students to use number cards and mental math to combine numbers to reach multiples of ten, which sometimes requires thinking about what to add to reach a target number.

Students set up and solve missing-addend equations such as 37 + __ = 40 and 24 + 6 = 30 by showing the starting number with unit blocks or an abacus and counting additional units to reach the next multiple of ten. Activity 3 explicitly asks, "What number should you add to 24 to get to 30?" and has students write number sentences (e.g., 46 + 4 = 50). The "What's Missing?" student page and answer key require students to determine the unknown addend in several two-digit equations (for example, 52 + 8 = 60 and __ + 25 = 30).

The lesson's Skills list explicitly includes "Determine the unknown whole number in an addition or subtraction equation relating three whole numbers," indicating students will work with unknowns in equations. Activity 2 has students solve and sort subtraction equations (for example, 10-5, 10-2) and the answer key groups subtraction facts under their results, showing students compute differences. The introduction asks students to identify which number sentence asks for a difference, prompting distinction between addition and subtraction tasks.

Students draw number cards 1–10 and name the number that combines with the drawn card to make 10 (for example, if they draw 3 they say "seven"). In the wrapping up activity, students flip cards 10, 20, …, 100 and say the number that adds to the shown number to make 100 (for example, flip 60 and say "forty"). The web game and practice sheets ask students to find missing addends to reach target sums (Facts to Make 100 and Facts to Make 20).