3.OA.8: Solve Two-Step Word Problems
Also written as 3.OA.D.8 and CCSS.MATH.CONTENT.3.OA.D.8 · Cluster: Solve problems involving the four operations, and identify and explain patterns in arithmetic.
The Official Wording
Solve two-step word problems using the four operations. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding.
Common Core State Standards, Grade 3, Operations & Algebraic Thinking · Read it at the source · Checked October 14, 2026
What 3.OA.8 Means in Plain English
Third graders solve stories that need two operations, like 4 packs of 6 juice boxes with 9 handed out at snack time. They write one equation with a letter for the unknown, (4 × 6) − 9 = j, and find j = 15.
Then they ask whether the answer is sensible: 24 rounds to 20 and 9 to 10, so about 10 should be left, and 15 is close. Fourth grade stretches this to more steps and to remainders that need interpreting (4.OA.3).
3.OA.8 I Can Statements
- I can decide which two steps a word problem needs.
- I can write an equation with a letter for the unknown.
- I can use rounding to check whether my answer makes sense.
3.OA.8 Worked Example
One library story: two steps, a letter for the unknown, and the rounding check the standard asks for.
The library got 6 boxes of new books with 9 books in each box. The librarian shelved 18 of them. How many books are still in boxes?
- Step one: how many books came in? 6 boxes of 9.6 × 9 = 54
- Step two: 18 went on the shelves. Call the books that are left b.54 − 18 = b
- Subtract by place value: 54 − 10 = 44, then 44 − 8 = 36.b = 36
- Written as one equation, the multiplication goes first.(6 × 9) − 18 = 36
Check it: Round: 54 is about 50 and 18 is about 20, so about 30 should be left. 36 is close, so the answer makes sense.
Common Mistakes with 3.OA.8
Stopping after step one
Answers 54 books, the number that arrived, not the number still in boxes
Try this: Have students underline the question and reread it after each step, asking “Is this the number the question wants?”
Adding every number in sight
6 + 9 + 18 = 33 books
Try this: Ask students to sketch each step before choosing an operation. Six boxes of 9 is equal groups, so it calls for multiplying.
Working left to right through a mixed equation
18 + 6 × 9 worked as 24 × 9 = 216
Try this: Write each step as its own equation first, or put parentheses around the multiplication so everyone does it before adding.
Where 3.OA.8 Fits
Practice 3.OA.8
Quick Check
- Ana has 3 bags of 8 marbles. She gives away 5. How many marbles does she have now?
- 28 students go on a trip and 4 more join. They ride in vans that hold 8 each. How many vans?
- Write an equation with a letter, then solve: Leo had 50 stickers and bought 2 packs of 10.