Ahava~Love Assembly

Grade 2 Mathematics Week 18 | Teacher Guide

Grade 2 | MATHEMATICS

WEEK 18 • TEACHER GUIDE AND ANSWER KEY • DAYS 86–90

Read each lesson aloud with the child and model the worked example before practice. Do not show this key during practice. Accept oral, drawn or written answers where the child cannot yet write the whole answer. On Day 90, read aloud if needed but give no hints.

Week 18 Student Textbook | Week 18 Practice Workbook | Week 18 Teacher Guide | Week 17 Student Textbook | Week 19 Student Textbook | Grade 2 index

Day 86: Hundreds, Tens and Ones in New Ways

Standard: Grade 2 Math Standard 6, 2.NBT.A.6; Grade 2 Math Standard 6, 2.NBT.A.6a

Practice figure: Base-ten blocks: Numbers A and B, printed on the Week 18 Practice Workbook. A: 2 hundreds, 4 tens, 5 ones. B: 1 hundred, 10 tens, 3 ones.

Worked example: What number is 3 hundreds, 5 tens and 2 ones? Worked answer: 352.

  1. 245.
  2. 203 (10 tens is 1 more hundred, so 2 hundreds and 3 ones).
  3. 40 tens.
  4. 706.
  5. 10 tens is 10 groups of 10, and 10 groups of 10 is 100. Accept any answer showing that ten tens make one hundred, such as counting by tens to 100.

Teaching note: Number B is a trading problem on purpose: watch for children who write 1103 or 113. Have them trade 10 tens for 1 hundred with real or drawn blocks.

Day 87: Count Within 1000 and Skip-Count

Standard: Grade 2 Math Standard 7, 2.NBT.A.7

Practice figure: Number line: count by 5s, printed on the Week 18 Practice Workbook. Ticks every 5 from 385 to 420. Labeled: 385, 390, 405, 415, 420. Empty boxes at 395, 400 and 410.

Worked example: Count by 5s: 45, 50, 55, what comes next? Worked answer: 60.

  1. 395, 400, 410.
  2. 700, 710.
  3. 250, 350, 450, 550, 650, 750.
  4. 1000.
  5. 690 has 9 tens. Adding 1 more ten makes 10 tens, which is 1 hundred, so 6 hundreds becomes 7 hundreds and the tens digit becomes 0. Accept any answer about 10 tens making a new hundred.

Teaching note: Practice counting aloud across hundreds before the written items. 1000 is the end of the grade 2 counting range.

Day 88: Read, Write and Compare Numbers

Standard: Grade 2 Math Standard 8, 2.NBT.A.8; Grade 2 Math Standard 9, 2.NBT.A.9

Worked example: Write 735 in expanded form. Worked answer: 700 + 30 + 5.

  1. 500 + 8 (or 500 + 0 + 8).
  2. 462.
  3. 381 > 318.
  4. 607 < 670, so 600 + 7 < 670.
  5. You must compare the hundreds first. 299 has 2 hundreds and 301 has 3 hundreds, so 301 is greater. Lena compared the ones instead.

Teaching note: For 508, accept 500 + 0 + 8; the zero shows there are no tens.

Day 89: Hands-On: Number-Card Game

Standard: Grade 2 Math Standard 9, 2.NBT.A.9; Grade 2 Math Standard 13, 2.NBT.B.13

Worked example: What is 10 less than 300? Worked answer: 290.

  1. 505.
  2. 212.
  3. 742.
  4. 247.
  5. 742 > 247. I checked the hundreds first: 7 hundreds is more than 2 hundreds.

Teaching note: Use the observation checklist below. Answers in the game tables vary with the cards drawn.

Hands-on task observation checklist (Number-card game). Check each item you observe. Four or five items shows the child met the task goal; two or three means repeat the task with support.

  • ☐ Child made a three-digit number from the cards each round.
  • ☐ Child wrote 10 more and 10 less correctly.
  • ☐ Child wrote 100 more and 100 less correctly.
  • ☐ Child compared the two numbers with the correct sign.
  • ☐ Child explained which place they compared first.

Day 90: Independent Check: Place Value

Standard: Grade 2 Math Standard 6, 2.NBT.A.6; Grade 2 Math Standard 6, 2.NBT.A.6a; Grade 2 Math Standard 7, 2.NBT.A.7; Grade 2 Math Standard 8, 2.NBT.A.8; Grade 2 Math Standard 9, 2.NBT.A.9; Grade 2 Math Standard 13, 2.NBT.B.13

Practice figure: Base-ten blocks: Numbers C and D, printed on the Week 18 Practice Workbook. C: 3 hundreds, 0 tens, 8 ones. D: 0 hundreds, 12 tens, 4 ones.

Worked example: How many hundreds are in 600? Worked answer: 6.

  1. 308.
  2. 124 (12 tens is 1 hundred and 2 tens).
  3. 430.
  4. 589 < 598.
  5. 903. 893 has 9 tens; 1 more ten makes 10 tens, which is a new hundred, so 8 hundreds becomes 9 hundreds and the tens digit becomes 0.

Teaching note: Independent check: read aloud if needed, but give no hints.

Week 18 Student Textbook | Week 18 Practice Workbook | Week 18 Teacher Guide | Week 17 Student Textbook | Week 19 Student Textbook | Grade 2 index