Lesson 14

Math

Unit 1

Lesson 14 of 14

## Objective

Solve one- and two-step word problems involving addition and subtraction, using rounding to assess the reasonableness of answers.

## Common Core Standards

### Core Standards

• 3.NBT.A.1 — Use place value understanding to round whole numbers to the nearest 10 or 100.
• 3.NBT.A.2 — Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
• 3.OA.D.8 — 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. This standard is limited to problems posed with whole numbers and having whole-number answers; students should know how to perform operations in the conventional order when there are no parentheses to specify a particular order (Order of Operations).

• 2.NBT.B.7
• 2.OA.A.1

## Criteria for Success

1. Solve one- and two-step word problems involving addition and subtraction (MP.4).
2. Represent word problems using equations (see Tips for Teachers) (MP.2).
3. Use rounding to estimate the answer to a two-step problem in each of the following cases:
• Use rounding to assess the reasonableness of one’s own or someone else’s answer (MP.1).
• Use rounding when an exact answer is not needed or expected (e.g., the problem says "about" or "approximately").

## Tips for Teachers

• Lesson 14 is the first lesson of the year where students will solve two-step word problems. By the end of the year, students are expected to “represent these problems using equations with a letter standing for the unknown quantity” (3.OA.8). While they will write a single equation to represent some two-step problems by the end of the year, they should not be asked to do so in this lesson. Instead, they can write one equation for each step. This is because students have not yet encountered parentheses, which play an important role in many multi-step equations. Students will be introduced to parentheses in Unit 3, at which point they will represent two-step word problems with a single equation in limited cases.
• This lesson provides an opportunity to connect two domains in the grade, 3.OA and 3.NBT, since students will be solving one- and two-step word problems involving addition and subtraction, assessing the reasonableness of their answers using rounding.
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### Problem 1

Ms. Needham is fastening papers together for report card conferences. Here's what she's using:

There are 225 paper clips in the box to the left. Ms. Needham has already used 771 staples from the box on the right.

a.   How many staples are there remaining in the box on the right?

b.   Use your answer in Part (a) to write a second problem for your classmate to solve.

### Problem 2

Mary read 342 pages in July and 231 pages in August. This was 174 more pages than she needed to read for her school’s summer reading challenge. How many pages was she supposed to read for the summer reading challenge? Solve. Then assess the reasonableness of your answer.

### Problem 3

Mrs. Ingall is going to a hockey game. She has $139 in her pocket and wants to take out more cash to be able to pay for everything at the game. She will have to pay$268 for the tickets, $18 for a cab ride to the game, and$55 for food and drinks while she’s there. Approximately how much money should Mrs. Ingall take out of the bank to cover her costs?

## Problem Set

Unlock the answer keys for this lesson's problem set and extra practice problems to save time and support student learning.

### Discussion of Problem Set

• Look at #2. How close was your estimate? Was it too high or too low? Why?Â
• Look at #3. How did you determine which estimate was closest to the total number of pages James read last month? Were there any answers you were able to eliminate pretty easily? Why?Â
• Look at #4. How did you solve (a)? Was your answer reasonable? Why or why not?
• Look at #5. If you had been asked to round to the nearest hundred, how would that have changed your answer to Part (a)? Part (b)? Part (c)?Â
• Even though you werenâ€™t asked to estimate in #6, did anyone do so as a way to check the reasonableness of your answer?Â

There were 485 Red Sox fans and some Yankees fans in Fenway Park at a baseball game. In all, there were 649 fans at Fenway. Then 28 more Yankees fans came to Fenway.

a.   How many Yankee fans are at Fenway in total?

#### Student Response

The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

### Extra Practice Problems

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### Word Problems and Fluency Activities

Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

Lesson 13

## Lesson Map

Topic A: Foundations of Place Value

Topic B: Rounding to the Nearest Ten and Hundred

Topic C: Addition and Subtraction Within 1,000

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