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Place Value Power

A comprehensive third-grade mathematics unit covering place value representations up to 10,000, rounding to the nearest ten with benchmark values and number lines, and real-world word problems using algebraic equations and bar models.

Ccraig.buckler

Place Value Power

A comprehensive third-grade mathematics unit covering place value representations up to 10,000, rounding to the nearest ten with benchmark values and number lines, and real-world word problems using algebraic equations and bar models.

Ccraig.buckler
40

Number Line Check: The point for 43 is 3 units to the right of 40 and 2 units to the left of the midpoint 45. Since 43 is 3 units from 40 and 7 units from 50, it rounds to 40.

Level 2 • Developing Key Rounding 64 and 65 (The Midpoint Rule)

A. 64 rounded: 60

Circle: less than 5 (4 < 5, rounds down).

B. 65 rounded: 70

Circle: UP (5 in ones place rounds up).

Key Rule: 65 is equidistant from 60 and 70 (5 units away from both). Mathematical rule dictates that half-way values always round UP to the greater ten.

Level 3 • Proficient Key Special Cases: Single-Digit 8 & Century 97

Case 1: 1-Digit Number 8

• Two benchmark tens: 0 and 10

• Halfway mark: 5

• 8 rounded to nearest ten: 10

Case 2: 2-Digit Number 97

• Two benchmark tens: 90 and 100

• Halfway mark: 95

• 97 rounded to nearest ten: 100

Misconception Alert: Students often struggle with 8 because 0 is not recognized as a multiple of ten. For 97, students must see that rounding up creates a regrouping into the hundreds place (10 tens = 100).

Level 4 • Challenge Key Reverse Rounding Solution Set (Rounds to 80)

A. Complete Set of Numbers:

75, 76, 77, 78, 79, 80, 81, 82, 83, 84

Smallest: 75 Largest: 84

B. Boundary Reasoning:

• 74 is less than halfway (75), so it rounds down to 70.
• 85 reaches the midpoint between 80 and 90, so it rounds up to 90.

Place Value Power • Answer Key & Rubric Page 2 • Standard 3.NS.6

Teacher Solutions & Scoring Guide

Word Problems Answer Key

TEACHER COPY

Standard 3.CA.2: Real-World Problem Structures • Solution & Model Guide

Key • Page 3

Level 1 • Basic Key Join: 245 Honeycrisp + 188 Gala

Bar Model Structure:

Total Whole: □ (or t)

Part 1: 245

Part 2: 188

Equation & Solution:

245 + 188 = □

Calculation: 245 + 188 = 433

Answer: 433 bushels

Level 2 • Developing Key Part-Part-Whole: 512 Total, 268 Hot Lunch

Completed Model:

Total: 512 Students

Hot: 268

Home: 244

Equation & Solution:

268 + □ = 512 or 512 − 268 = □

Calculation: 512 − 268 = 244

Answer: 244 students

Level 3 • Proficient Key Compare: Room 14 (425 cans) vs Room 16 (289 cans)

Comparison Model Structure:

Room 14: 425 cans

Room 16: 289

d = 136

Equation & Solution:

425 − 289 = d or 289 + d = 425

Calculation: 425 − 289 = 136

Answer: 136 more cans

Level 4 • Challenge Key Multi-Step: Start 140, Baked c, Sold 85, Remained 195

A. Single Algebraic Equation:

140 + c − 85 = 195

(also accept: 140 + c = 195 + 85)

B. Value of Unknown c:

c = 140 new croissants

Worked Steps: Method 1: 140 − 85 = 55. Then 55 + c = 195 → c = 195 − 55 = 140.
Method 2 (Working Backwards): Before selling 85, there were 195 + 85 = 280. Since they started with 140: 280 − 140 = 140.

Place Value Power • Answer Key & Rubric Page 3 • Standard 3.CA.2

Bar Model / Tape Diagram:

Equation with Symbol (□):

Final Answer:

Pencils left:   pencils.

Level 2 • Developing Part-Part-Whole Structure • Unknown Part

Two third-grade classes collected 460 bottle caps for art. Mrs. Clark's class collected 245 caps. How many did Mr. Patel's class collect?

Complete Part-Part-Whole Model:

Total: 460 Bottle Caps

Clark: 245

Patel: ?

Equation with Symbol (p or □):

Final Answer:

Mr. Patel's class:   caps.

Level 3 • Proficient Comparison Structure • Unknown Difference

On Saturday, the Ferris wheel had 524 riders and the carousel had 378 riders. How many fewer riders did the carousel have?

Comparison Bar Model:

Equation with Variable (d):

Final Answer:

Difference:   riders.

Level 4 • Challenge Multi-Step Algebraic Structure • Unknown Change

An animal shelter had 210 bags of dog food. They received a delivery (s). They used 135 bags. At the end of the week, 225 bags remained.

A. Equation using symbol s:

B. Value of unknown s:

Delivery:   bags.

Show step-by-step calculations:

Place Value Power • Targeted Practice Page 2 • Standard 3.CA.2

Teacher Solutions & Scoring Guide

Word Problems Answer Key

TEACHER COPY

Standard 3.CA.2: Word Problems with Unknowns • Solution & Model Guide

Key • Part 2

Level 1 • Basic Key Take Away: 375 Start − 142 Sold

Tape Diagram Structure:

Total Started: 375 Pencils

Sold: 142

Left: □ = 233

Equation & Solution:

375 − 142 = □ or 142 + □ = 375

Calculation: 375 − 142 = 233

Answer: 233 pencils

Level 2 • Developing Key Part-Part-Whole: 460 Total, 245 Clark

Completed Model:

Total: 460 Bottle Caps

Clark: 245

Patel: p = 215

Equation & Solution:

245 + p = 460 or 460 − 245 = p

Calculation: 460 − 245 = 215

Answer: 215 bottle caps

Level 3 • Proficient Key Compare: Ferris Wheel (524) vs Carousel (378)

Comparison Model:

Ferris Wheel: 524 riders

Carousel: 378

d = 146

Equation & Solution:

524 − 378 = d or 378 + d = 524

Regrouping: 524 − 378 = 146

Answer: 146 fewer riders

Level 4 • Challenge Key Multi-Step: Start 210 + Delivery s − 135 Used = 225

A. Single Algebraic Equation:

210 + s − 135 = 225

(also accept: 210 + s = 225 + 135)

B. Value of Unknown s:

s = 150 bags

Calculation Steps & Check: Step 1: Combine knowns: 210 − 135 = 75.
Step 2: 75 + s = 225 → s = 225 − 75 = 150 bags.
Check: 210 + 150 = 360 bags total. 360 − 135 = 225 bags. Matches problem statement!

Place Value Power • Targeted Answer Key Page 2 • Standard 3.CA.2

A. Equation showing start (b):

B. Starting Beads:

Started with:   beads.

C. Concept Justification: Why do we ADD the remaining and sold beads to find the starting number?

Level 5 • Master Challenge Multi-Step Comparative & Unknown Change

Problem 5: Maya earned 280 carnival tickets. Her brother Caleb earned 95 fewer tickets than Maya. Later, Caleb won a mystery bonus round of tickets (t). Now Caleb has 240 tickets in all.

Step 1: Caleb's Tickets Before Bonus:

Equation: 280 − 95 = c

Caleb had:   tickets.

Step 2: Mystery Bonus Tickets (t):

Equation: c + t = 240

Bonus t =   tickets.

Complete Summary Sentence:

Caleb started with   tickets and won   bonus tickets.

Place Value Power • Word Problem Quest Page 2 • Standard 3.CA.2

Level 5 • Master Challenge Key Two-Step: Maya (280) → Caleb (−95) → Caleb (+t) = 240

Step 1: Caleb Before Bonus

Maya has 280; Caleb has 95 fewer:

280 − 95 = 185 tickets

Step 2: Mystery Bonus (t)

Caleb started with 185, ended with 240:

185 + t = 240 → t = 240 − 185 = 55

Summary & Verification: Caleb started with 185 tickets and won 55 bonus tickets. Check: 185 + 55 = 240 tickets. Full equation: (280 − 95) + t = 240.

Place Value Power • Word Problem Quest Key Page 2 • Standard 3.CA.2

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