1st Grade · Word Problems · Little Newtons
Word Problems Mixing Addition and Subtraction: Which Operation and Why
A first grade lesson that gives your child a real method — not a guessing game — for choosing between plus and minus. Action keywords, the parts-and-whole model, and 20 practice questions with step-by-step solutions. Aligned to Common Core 1.OA.A.1 and 1.OA.A.2. Free from SOMATH, an Upper West Side NYC math school.
Most first graders can add. Most first graders can subtract. What trips them up is the story problem where they have to decide which one to do — and where both operations show up in one paragraph. This lesson gives your child a two-question routine that works every time, plus 20 practice problems that mix addition and subtraction on purpose.
What is in this lesson
The two-question routine that always works
Before your child touches the numbers, they should ask two questions in this order:
1. What am I looking for — the whole or a part?
Every 1st grade addition/subtraction story fits into one picture: a whole broken into two parts.
- If both parts are known and the whole is missing → ADD
- If the whole and one part are known and the other part is missing → SUBTRACT
2. What is the action in the story?
Stories usually describe an action: putting things together, taking some away, comparing two amounts, or finishing with a total. The action confirms what the parts-and-whole picture already suggests.
- ADD when the action combines, joins, gets more, arrives, or gives a total.
- SUBTRACT when the action takes away, gives away, loses, breaks, eats, or compares.
Action-word clues (with a warning at the bottom)
These are the words that most reliably signal each operation for a 1st grader:
| Signals ADD (+) | Signals SUBTRACT (−) |
|---|---|
| in all, altogether, in total, joined | left, remain, still have, have now |
| together, both, plus, and | gave away, gave to, sold, ate, lost, broke |
| more arrived, more came, added | took away, threw away, spilled |
| combined, joined, put together | how many more, how many fewer, difference |
| the total, the sum, the whole | how much longer, how much shorter |
Three keyword traps that fool most 1st graders
Practice — Easy (Q1–Q8)
Warm-ups. Each problem uses one operation only.
Q1Easy
Maya has 6 crayons. Her teacher gives her 3 more crayons. How many crayons does Maya have in all?
Operation: + Answer: 9 crayons
6 + 3 = 9Q2Easy
Nico had 10 grapes. He ate 4 of them. How many grapes are left?
Operation: − Answer: 6 grapes
10 − 4 = 6Q3Easy
There are 5 red apples and 7 green apples in a bowl. How many apples are there in all?
Operation: + Answer: 12 apples
5 + 7 = 12Q4Easy
Isabela had 15 stickers. She gave 8 to her sister. How many stickers does she have now?
Operation: − Answer: 7 stickers
15 − 8 = 7Q5Easy
Diego caught 8 fish in the morning and 6 fish in the afternoon. How many fish did he catch altogether?
Operation: + Answer: 14 fish
8 + 6 = 14Q6Easy
A bakery had 20 cupcakes. They sold 13. How many cupcakes are left?
Operation: − Answer: 7 cupcakes
20 − 13 = 7Q7Easy
There are 9 kids on a bench. 4 more kids sit down. How many kids are on the bench now?
Operation: + Answer: 13 kids
9 + 4 = 13Q8Easy
Mateo had a jar with 18 candies. He gave 5 to his friend. How many candies are in the jar now?
Operation: − Answer: 13 candies
18 − 5 = 13Practice — Medium, mixed operations (Q9–Q16)
Now the story tells you both an addition and a subtraction, or hides which operation to use behind a tricky keyword. Your child has to pick.
Q9Medium
Ava had 7 balloons. She got 4 more at a party. Then 3 balloons popped. How many balloons does she have now?
Operations: + then − Answer: 8 balloons
Step 1: 7 + 4 = 11 Step 2: 11 − 3 = 8Q10Medium
Sam has 12 baseball cards. His brother gives him 6 more. How many baseball cards does Sam have in all?
Operation: + Answer: 18 cards
12 + 6 = 18Q11Medium
There were 14 birds on a fence. 5 of them flew away. How many birds are on the fence in all now?
Operation: − Answer: 9 birds
14 − 5 = 9Q12Medium
Sofia read 6 pages in the morning and 8 pages in the afternoon. Her book has 20 pages total. How many pages does she still have left to read?
Operations: + then − Answer: 6 pages
Step 1 (pages read): 6 + 8 = 14 Step 2 (pages left): 20 − 14 = 6Q13Medium
A pet store had 17 fish. They sold 9 fish on Monday. On Tuesday, 4 new fish arrived. How many fish are in the store now?
Operations: − then + Answer: 12 fish
Step 1 (after Monday): 17 − 9 = 8 Step 2 (after Tuesday): 8 + 4 = 12Q14Medium
Liam has 11 toy cars. Tomás has 4 toy cars. How many toy cars do the two boys have together?
Operation: + Answer: 15 cars
11 + 4 = 15Q15Medium
Emma had 13 pencils. She lost 2 at school and gave 3 to her cousin. How many pencils does she have now?
Operation: − twice Answer: 8 pencils
Step 1: 13 − 2 = 11 Step 2: 11 − 3 = 8 Shortcut: 13 − (2 + 3) = 13 − 5 = 8Q16Medium
A classroom has 8 boys and 9 girls. 2 kids go home early. How many kids are still in the classroom?
Operations: + then − Answer: 15 kids
Step 1 (total): 8 + 9 = 17 Step 2 (after 2 leave): 17 − 2 = 15Practice — Harder, compare & two-step (Q17–Q20)
Compare problems ("how many more") always look like addition but need subtraction. Two-step problems mix both operations in one story.
Q17Hard
Ana has 16 stickers. Ben has 9 stickers. How many more stickers does Ana have than Ben?
Operation: − Answer: 7 more stickers
16 − 9 = 7Q18Hard
A ribbon is 18 inches long. Maria cuts off 5 inches, then cuts off 4 more inches. How many inches of ribbon does she have left?
Operation: − twice Answer: 9 inches
Step 1: 18 − 5 = 13 Step 2: 13 − 4 = 9 Shortcut: 18 − (5 + 4) = 18 − 9 = 9Q19Hard
Julia has 6 dollars. Her grandma gives her 8 more dollars for her birthday. She then spends 5 dollars on a book. How much money does Julia have left?
Operations: + then − Answer: $9
Step 1 (after birthday): 6 + 8 = 14 Step 2 (after buying book): 14 − 5 = 9Q20Hard
Class A has 19 students. Class B has 14 students. 3 students moved from Class A to Class B. Which class has more students now, and by how many?
Operations: −, +, then − Answer: Class B has 1 more student
Class A now: 19 − 3 = 16 Class B now: 14 + 3 = 17 Compare: 17 − 16 = 1 → Class B has 1 more.Answer key — all 20 questions
| Q | Operation | Answer | Q | Operation | Answer |
|---|---|---|---|---|---|
| 1 | + | 9 | 11 | − | 9 |
| 2 | − | 6 | 12 | + then − | 6 |
| 3 | + | 12 | 13 | − then + | 12 |
| 4 | − | 7 | 14 | + | 15 |
| 5 | + | 14 | 15 | − twice | 8 |
| 6 | − | 7 | 16 | + then − | 15 |
| 7 | + | 13 | 17 | − | 7 |
| 8 | − | 13 | 18 | − twice | 9 |
| 9 | + then − | 8 | 19 | + then − | 9 |
| 10 | + | 18 | 20 | −, +, − | Class B has 1 more student |
The three big ideas your child should walk away with
- Ask "whole or part?" first. If both parts are given, add. If the whole and one part are given, subtract. Draw the picture.
- Use keywords as a hint, not a rule. "In all," "together," "altogether" usually mean add. "Left," "gave," "sold," "how many more" usually mean subtract. Always confirm with the parts-and-whole picture.
- Two actions = two steps. If the story has both "got more" and "gave away," the child should do the operations one at a time, in the order the story tells them.
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