Mississippi Math 3.OA.8

Math3rd GradeOperations and Algebraic Thinking (OA) Represent and Solve Problems Involving Multiplication and Division

The Standard

Solve two-step (two operational steps) 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 rounding3. Include problems with whole dollar amounts.

2025 Mississippi College- and Career-Readiness Standards for Mathematics · Solve problems Involving the Four Operations, and Identify and Explain Patterns in Arithmetic

Teacher's field guide

What This Standard Means

What Students Need to Do: Students choose two operations that fit a word problem and write an equation with a letter for the unknown. They solve problems with counts or whole dollar amounts, then check answers by mental math or rounding.
What Mastery Looks Like: Given three $9 notebooks and $50 to spend, a student writes m = 50 - 3 × 9 and finds $23 left. They round $9 to $10 and explain why $23 is close to the estimated $20.
Common Misconceptions: Students may use the numbers in the order they appear, even when they need to multiply before subtracting. Some use the letter as a label rather than an unknown, or give a rounded estimate as the exact answer.
How to Assess It: Ask: “Mia has $50 and buys three notebooks for $9 each. How much is left? Write an equation with m for the money left, solve it, and check by rounding $9 to $10.”

Lesson moves

Ways to Teach It

Give pairs $50 in play money and three $9 price tags; have them pay, count change, and write an equation.
Ask, “Why do we multiply 3 × 9 before subtracting from 50 when buying three $9 notebooks with $50?”
Write cards like “3 boxes of 8 markers, then 5 more”; partners race to write a letter equation and solve each.
Plan buses for 28 students, 7 per bus, at $20 per bus; find the total cost and check mentally.

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