Addition & Subtraction Word Problems Within 20 | 1st Grade Math

Addition and Subtraction Word Problems Within 20 - Grade 1 Math
Grade 1 Math  ›  Addition & Subtraction  ›  Lesson 16
Grade 1 Math - Addition and Subtraction

Addition & Subtraction Word Problems Within 20

Learn how to solve first grade addition and subtraction word problems within 20. Students practice add-to, take-from, put-together, take-apart, and compare situations with the unknown in different positions.

Read the story carefully, decide what is happening, use a drawing or model when helpful, write an equation, solve, and check whether the answer makes sense.

Word problems within 20 Addition word problems Subtraction word problems Unknowns in different positions 1st Grade Math

๐ŸŽฏ What You Will Learn

Understand what the story is asking
Decide whether amounts are joining, separating, forming parts of a whole, or being compared.
Represent the story
Use objects, a drawing, a part-part-whole model, or a comparison model when helpful.
Write an equation
Use addition or subtraction and place the unknown where it belongs in the story.
Solve and check
Find the answer, put it back into the story, and decide whether it is reasonable.
For parents & teachers — standards alignment: This lesson directly addresses CCSS 1.OA.A.1: use addition and subtraction within 20 to solve add-to, take-from, put-together, take-apart, and compare word problems with unknowns in all positions. It also supports CCSS 1.OA.C.6 and 1.OA.D.8 through addition/subtraction strategies and unknown-number equations. Texas alignment includes TEKS 1.3(B), 1.3(E), 1.3(F), 1.5(D), and 1.5(F), emphasizing models, number sentences, strategy explanations, generated problem situations, and unknowns in different positions.

๐Ÿง  Key Vocabulary

word problem — a math situation told with words.
unknown — the number we need to find.
equation — a mathematical statement that shows two values are equal.
total — the amount altogether.
part — one amount that belongs to a whole.
difference — how far apart two amounts are, or the result of subtraction.

๐Ÿ“š Four Important Story Types

First grade word problems are not all the same. Understanding the story is more useful than searching for a single keyword.

➕ Add To An amount starts, then more joins it. The start, change, or result may be unknown.
➖ Take From An amount starts, then some leaves or is removed. Any of the three amounts may be unknown.
๐Ÿงฉ Put Together / Take Apart Two parts make one whole. You may need to find the whole or a missing part.
⚖️ Compare Two amounts are compared. You may need the difference, the bigger amount, or the smaller amount.
Do not rely on keywords alone. A word such as “more” does not always mean that you should simply add the two visible numbers. Read the whole story and decide what each number represents.

๐Ÿ› ️ A Four-Step Problem-Solving Routine

1 Read What is happening in the story?
2 Model Draw, act it out, or show the parts if that helps.
3 Write & solve Write an equation and find the unknown.
4 Check Does the answer fit the story?

๐Ÿงฉ Two Useful Models

Part-Part-Whole If 5 are red and 7 are blue, the two parts make one whole.
Part: 5
Part: 7
Whole: 12
Compare Two Amounts If one child has 12 stickers and another has 8, the extra part is the difference.
12 stickers
8 stickers
Difference: 4
Helpful question: before choosing an operation, ask: “What do I know, what changed or what is being compared, and what am I trying to find?”

๐ŸŒŸ 25 Worked Examples

Try each story first. Then open “Show solution” to compare your reasoning.
1 Add to: result unknown
Mia has 7 apples. Her dad gives her 5 more apples. How many apples does Mia have now? 7 + 5 = □
Show solution Hide solution

Mia starts with 7 and gets 5 more, so we add. 7 + 5 = 12. Mia has 12 apples now. Check: 12 is greater than 7, which makes sense because apples were added.

2 Add to: change unknown
Noah has 6 toy cars. He gets some more. Now he has 14 toy cars. How many toy cars did he get? 6 + □ = 14
Show solution Hide solution

The starting amount is 6 and the new total is 14. Find the missing part: 14 − 6 = 8. Noah got 8 toy cars. Check: 6 + 8 = 14.

3 Add to: start unknown
Ava had some stickers. She got 4 more stickers and then had 11. How many stickers did she have at first? □ + 4 = 11
Show solution Hide solution

The starting amount is unknown. Think: what number plus 4 makes 11? Since 7 + 4 = 11, Ava had 7 stickers at first.

4 Take from: result unknown
There are 15 cookies on a plate. Six cookies are eaten. How many cookies are left? 15 − 6 = □
Show solution Hide solution

The story starts with 15 and 6 are taken away, so subtract. 15 − 6 = 9. There are 9 cookies left.

5 Take from: change unknown
There are 13 balloons. Some balloons pop. Eight balloons are left. How many balloons popped? 13 − □ = 8
Show solution Hide solution

We know the start and the amount left. Find the missing change: 13 − 8 = 5. So 5 balloons popped. Check: 13 − 5 = 8.

6 Take from: start unknown
Some birds are on a fence. Seven fly away, and 6 birds remain. How many birds were on the fence at first? □ − 7 = 6
Show solution Hide solution

The starting number is unknown. Put the two known parts back together: 6 + 7 = 13. There were 13 birds at first. Check: 13 − 7 = 6.

7 Put together: total unknown
A box has 8 red crayons and 5 blue crayons. How many crayons are in the box altogether? 8 + 5 = □
Show solution Hide solution

The red crayons and blue crayons are two parts of one total. Add the parts: 8 + 5 = 13. There are 13 crayons altogether.

8 Put together: one part unknown
There are 16 marbles altogether. Nine are green and the rest are yellow. How many marbles are yellow? 9 + □ = 16
Show solution Hide solution

The whole is 16 and one part is 9. Find the missing part: 16 − 9 = 7. There are 7 yellow marbles.

9 Take apart: find the other part
There are 14 books on a shelf. Six are storybooks and the rest are picture books. How many are picture books? 14 − 6 = □
Show solution Hide solution

The total is 14. One part is 6. Subtract to find the other part: 14 − 6 = 8. There are 8 picture books.

10 Compare: difference unknown
Lena has 12 beads. Sam has 8 beads. How many more beads does Lena have than Sam? 12 − 8 = □
Show solution Hide solution

We compare the two amounts and find the difference. 12 − 8 = 4. Lena has 4 more beads than Sam.

11 Compare: bigger amount unknown
Leo has 6 shells. Emma has 7 more shells than Leo. How many shells does Emma have? 6 + 7 = □
Show solution Hide solution

Emma has Leo's 6 shells plus 7 more. 6 + 7 = 13. Emma has 13 shells.

12 Compare: smaller amount unknown
Ava has 17 pencils. Ben has 5 fewer pencils than Ava. How many pencils does Ben have? 17 − 5 = □
Show solution Hide solution

Ben has 5 fewer than 17, so subtract: 17 − 5 = 12. Ben has 12 pencils.

13 Choose the operation: add
Nine ducks are in a pond. Three more ducks swim over. How many ducks are in the pond now?
Show solution Hide solution

The amount grows because more ducks join. Write 9 + 3 = 12. There are 12 ducks in the pond.

14 Choose the operation: subtract
Eighteen blocks are in a bin. Seven blocks are taken out. How many blocks remain?
Show solution Hide solution

The amount gets smaller because blocks are taken away. Write 18 − 7 = 11. 11 blocks remain.

15 Use a drawing or mental picture
There are 9 stars on one card and 8 stars on another card. How many stars are there altogether?
Show solution Hide solution

The two groups are put together. Add 9 + 8 = 17. There are 17 stars altogether. A drawing of two groups can help you see the parts.

16 Use a related fact to check
Five children are at a table. Nine more children join them. How many children are at the table now?
Show solution Hide solution

Add 5 + 9 = 14. There are 14 children. Check with subtraction: 14 − 9 = 5, so the answer fits the story.

17 Find the missing amount taken away
There are 16 oranges in a basket. Some are used for juice, and 9 oranges remain. How many oranges were used?
Show solution Hide solution

Write 16 − □ = 9. The missing amount is 7 because 16 − 7 = 9. So 7 oranges were used.

18 Find the unknown starting amount
Some frogs are near a pond. Six more frogs arrive, and then there are 15 frogs. How many frogs were there at first?
Show solution Hide solution

Write □ + 6 = 15. The missing starting amount is 9 because 9 + 6 = 15. There were 9 frogs at first.

19 Compare: how many fewer?
One jar has 16 buttons. Another jar has 9 buttons. How many fewer buttons are in the second jar?
Show solution Hide solution

Find the difference between 16 and 9: 16 − 9 = 7. The second jar has 7 fewer buttons.

20 Put together and write an equation
A garden has 10 red flowers and 4 yellow flowers. How many flowers are there in all?
Show solution Hide solution

The groups are joined, so add. Write 10 + 4 = 14. There are 14 flowers in all.

21 Take from and check
Twelve fish are in a tank. Three fish are moved to another tank. How many fish stay in the first tank?
Show solution Hide solution

Subtract because fish are moved away: 12 − 3 = 9. 9 fish stay. Check: 9 + 3 = 12.

22 Part-part-whole: missing part
There are 12 hats. Four are red and the rest are blue. How many hats are blue?
Show solution Hide solution

The whole is 12 and one part is 4. Write 4 + □ = 12 or 12 − 4 = □. Since 12 − 4 = 8, there are 8 blue hats.

23 Take from: result after a larger change
There are 19 toy dinosaurs. Eight are put away. How many toy dinosaurs are still out?
Show solution Hide solution

Subtract the amount put away: 19 − 8 = 11. There are 11 toy dinosaurs still out.

24 Add to and explain
Four children are on the playground. Nine more children come outside. How many children are on the playground now?
Show solution Hide solution

The group gets larger, so add: 4 + 9 = 13. There are 13 children now. The answer is larger than 4, which matches the story.

25 Mixed challenge: unknown change
There are 20 markers. Some are given to students, and 14 markers remain. How many markers were given away?
Show solution Hide solution

Write 20 − □ = 14. Find the missing change: 20 − 14 = 6. So 6 markers were given away. Check: 20 − 6 = 14.

๐ŸŽฎ Independent Practice — 30 Problems

  1. Two red birds and 6 blue birds are on a wire. How many birds are there altogether?
  2. Three children are reading. Seven more children join them. How many children are reading now?
  3. There are 10 toy boats. Four are red and the rest are blue. How many boats are blue?
  4. Five frogs are on a log. Six more frogs hop onto the log. How many frogs are there now?
  5. Eight stickers are on a page. Six more stickers are added. How many stickers are on the page now?
  6. Nine apples are in a bag. Seven more apples are added. How many apples are in the bag now?
  7. There are 15 pencils. Ten are yellow and the rest are green. How many pencils are green?
  8. A shelf has 11 books. Four more books are added. How many books are on the shelf now?
  9. A basket has 17 pieces of fruit. Twelve are apples and the rest are pears. How many pears are there?
  10. Thirteen children are on a bus. Six more children get on. How many children are on the bus now?
  11. There are 11 balloons. Two pop. How many balloons are left?
  12. Twelve cookies are on a tray. Five are eaten. How many cookies are left?
  13. There are 14 crayons. Five are put away. How many crayons remain?
  14. Fifteen ducks are in a pond. Four swim away. How many ducks remain?
  15. Sixteen blocks are in a box. Six are taken out. How many blocks remain?
  16. Seventeen shells are on a table. Eight are moved away. How many shells remain?
  17. Eighteen flowers are in a garden. Five are picked. How many flowers remain?
  18. Nineteen marbles are in a bag. Seven are removed. How many marbles remain?
  19. There are 20 toy cars. Nine are put in a drawer. How many toy cars are left out?
  20. There are 13 fish in a tank. Some are moved, and 9 remain. How many fish were moved? Write an equation with □ for the unknown and solve.
  21. Maya has 14 beads. Owen has 9 beads. How many more beads does Maya have than Owen?
  22. Liam has 18 cards. Zoe has 12 cards. How many fewer cards does Zoe have than Liam?
  23. Nina has 15 stickers. Kai has 10 stickers. How many more stickers does Nina have?
  24. Ava has 17 shells. Ben has 11 shells. How many fewer shells does Ben have?
  25. One tower has 20 blocks. Another tower has 13 blocks. How many more blocks are in the first tower?
  26. Seven birds are in a tree. Some more arrive, and then there are 16 birds. How many birds arrived?
  27. Some crayons are in a box. Eight more crayons are added, and then there are 19. How many crayons were in the box at first?
  28. Some children are playing. Six go home, and 12 children remain. How many children were playing at first?
  29. There are 20 apples. Some are used, and 13 remain. How many apples were used?
  30. Extension: The equation is 6 + 9 = 15. Write a short word problem that matches the equation.

๐Ÿ† Lesson Test — 15 Questions

  1. One box has 1 red ball and 8 blue balls. How many balls are there altogether?
  2. Two rabbits are in a yard. Nine more rabbits enter. How many rabbits are in the yard now?
  3. A jar has 14 buttons. Three are red and the rest are white. How many buttons are white?
  4. Some children are at an art table. Eight more children join them, and then there are 14 children. How many children were at the table at first? Write an equation with □ for the unknown and solve.
  5. Maya has 18 toy animals. Leo has 7 fewer toy animals than Maya. How many toy animals does Leo have?
  6. Fourteen birds are on a roof. Two fly away. How many birds remain?
  7. Sixteen apples are in a basket. Five are eaten. How many apples remain?
  8. Seventeen toy cars are on a mat. Some are put away, and 11 remain. How many toy cars were put away? Write an equation with □ for the unknown and solve.
  9. Eighteen pencils are on a table. Four are taken away. How many pencils remain?
  10. Twenty crayons are in a box. Eight are used. How many crayons remain?
  11. Luca has 12 blocks. Maya has 7 blocks. How many more blocks does Luca have?
  12. Seven fish are in a tank. Some more are added, and then there are 15 fish. How many fish were added?
  13. Some balloons are at a party. Five pop, and 10 balloons remain. How many balloons were there at first?
  14. There are 19 counters. Six are red and the rest are yellow. How many counters are yellow?
  15. Eli has 4 marbles. Ana has 8 more marbles than Eli. How many marbles does Ana have?

๐Ÿ” Complete Answer Key

Show practice answer key Hide practice answer key

Practice Answers

1. 8 birds; 2 + 6 = 8.
2. 10 children; 3 + 7 = 10.
3. 6 boats; 10 − 4 = 6.
4. 11 frogs; 5 + 6 = 11.
5. 14 stickers; 8 + 6 = 14.
6. 16 apples; 9 + 7 = 16.
7. 5 pencils; 15 − 10 = 5.
8. 15 books; 11 + 4 = 15.
9. 5 pears; 17 − 12 = 5.
10. 19 children; 13 + 6 = 19.
11. 9 balloons; 11 − 2 = 9.
12. 7 cookies; 12 − 5 = 7.
13. 9 crayons; 14 − 5 = 9.
14. 11 ducks; 15 − 4 = 11.
15. 10 blocks; 16 − 6 = 10.
16. 9 shells; 17 − 8 = 9.
17. 13 flowers; 18 − 5 = 13.
18. 12 marbles; 19 − 7 = 12.
19. 11 toy cars; 20 − 9 = 11.
20. 4 fish; 13 − □ = 9, so □ = 4. Check: 13 − 4 = 9.
21. 5 beads; 14 − 9 = 5.
22. 6 cards; 18 − 12 = 6.
23. 5 stickers; 15 − 10 = 5.
24. 6 shells; 17 − 11 = 6.
25. 7 blocks; 20 − 13 = 7.
26. 9 birds; 7 + 9 = 16.
27. 11 crayons; 11 + 8 = 19.
28. 18 children; □ − 6 = 12, so □ = 18. Check: 18 − 6 = 12.
29. 7 apples; 20 − □ = 13, so □ = 7. Check: 20 − 7 = 13.
30. Possible answer: Sam has 6 toy trains. He gets 9 more. Now he has 15 toy trains.
Show test answer key Hide test answer key

Test Answers

1. 9 balls; 1 + 8 = 9.
2. 11 rabbits; 2 + 9 = 11.
3. 11 buttons; 14 − 3 = 11.
4. 6 children; □ + 8 = 14, so □ = 6. Check: 6 + 8 = 14.
5. 11 toy animals; 18 − 7 = 11.
6. 12 birds; 14 − 2 = 12.
7. 11 apples; 16 − 5 = 11.
8. 6 toy cars; 17 − □ = 11, so □ = 6. Check: 17 − 6 = 11.
9. 14 pencils; 18 − 4 = 14.
10. 12 crayons; 20 − 8 = 12.
11. 5 blocks; 12 − 7 = 5.
12. 8 fish; 7 + 8 = 15.
13. 15 balloons; 15 − 5 = 10.
14. 13 counters; 19 − 6 = 13.
15. 12 marbles; 4 + 8 = 12.

๐Ÿ’ก Common Mistakes to Watch For

Choosing an operation from one keyword
Read the whole situation instead of automatically adding when you see “more.”
Assuming the unknown is always the result
The missing number may be the start, the change, a part, or one of the compared amounts.
Writing an equation that does not match the story
Say what each number represents before you write the equation.
Forgetting to answer the question
Include the correct unit or object: apples, birds, stickers, blocks, and so on.
What comes next: Lesson 17 focuses on addition and subtraction fluency within 10, using efficient strategies to build speed and accuracy with basic facts.

๐Ÿ”— Related Lessons

Lesson 14 — Missing Numbers & Unknowns Review how to find an unknown in different positions in addition and subtraction equations. Lesson 15 — Add Three Numbers Within 20 Review addition strategies and three-addend situations with totals within 20.

๐Ÿ–จ️ Printable Companion

A future Addition & Subtraction Word Problems Within 20 Practice Pack can include picture-supported stories, equation-matching tasks, unknown-position practice, compare problems, mixed review, and a complete answer key.

← Lesson 15: Add Three Numbers Within 20 Grade 1 Math Hub Next: Addition & Subtraction Fluency Within 10 →

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