Ahava~Love Assembly

Grade 2 Mathematics Week 17 | Teacher Guide

Grade 2 | MATHEMATICS

WEEK 17 • TEACHER GUIDE AND ANSWER KEY • DAYS 81–85

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 85, read aloud if needed but give no hints.

Week 17 Student Textbook | Week 17 Practice Workbook | Week 17 Teacher Guide | Week 16 Student Textbook | Grade 2 index

Day 81: Word Problems with an Unknown

Standard: Grade 2 Math Standard 1, 2.OA.A.1

Worked example: A nursery had 34 apple trees. Some more were planted. Now there are 61. How many were planted? Worked answer: 27 trees were planted.

  1. 84 seedlings (46 + 38 = 84).
  2. □ – 25 = 47. He had 72 trees (47 + 25 = 72).
  3. 34 more yards (63 – 29 = 34).
  4. 35 pecans (92 – 57 = 35, or 57 + □ = 92).
  5. The whole bar is the unknown start. One part is the 25 he sold and the other part is the 47 left, so the whole is 25 + 47 = 72. Accept a bar model with the two parts and the whole marked unknown.

Teaching note: Have the child say what each number means in the story before solving. Accept any correct equation form for the unknown.

Day 82: Two-Step Word Problems

Standard: Grade 2 Math Standard 1, 2.OA.A.1

Worked example: A crew laid 20 feet of railroad track before lunch and 15 feet after lunch. They need 60 feet. How many more feet must they lay? Worked answer: 25 more feet.

  1. 34 pecans (18 + 25 = 43, then 43 – 9 = 34).
  2. 37 feet (35 + 28 = 63, then 100 – 63 = 37).
  3. 61 berries (50 – 12 = 38, then 38 + 23 = 61).
  4. 24 songs (16 – 8 = 8 for Wren, then 16 + 8 = 24).
  5. 35 + 28 = 63 is the feet laid so far. 100 – 63 = 37 is the feet still to lay. Accept the two equations with the meaning of each answer (or 100 – 35 = 65 and 65 – 28 = 37).

Teaching note: In the Mockingbird problem, watch for children who add 16 + 8 = 24 without finding Wren’s number first; here that happens to give the right total, so ask them to tell how many songs Wren sang (8).

Day 83: Add and Subtract Within 1000

Standard: Grade 2 Math Standard 12, 2.NBT.B.12; Grade 2 Math Standard 12, 2.NBT.B.12a

Worked example: Solve 325 + 148. Worked answer: 473.

  1. 734 seedlings.
  2. 438.
  3. 436 holes.
  4. 326 copies.
  5. Add the answer to the number taken away: 438 + 365 = 803. Because it equals the starting number, the answer is right. Accept any answer that adds the difference and the subtracted number.

Teaching note: Problems 2 and 4 need trades across a zero. If the child struggles, model 803 – 365 with base-ten blocks: trade 1 hundred for 10 tens, then 1 ten for 10 ones.

Day 84: Make and Read a Bar Graph

Standard: Grade 2 Math Standard 16, 2.DA.A.16; Grade 2 Math Standard 16, 2.DA.A.16a

Practice figure: Bar graph: Our Favorite Kind (a sample survey), printed on the Week 17 Practice Workbook. Bar heights: Fable 5, Tall tale 8, Legend 4, Song 6.

Worked example: A bar graph shows 9 people chose apples and 4 chose pears. How many more chose apples? Worked answer: 5 more people.

  1. 8.
  2. 4 more (8 – 4).
  3. 11 (5 + 6).
  4. 15 (5 + 4 + 6 = 15, or 23 – 8 = 15).
  5. I added all the bars to get 23 people, then took away the 8 who chose tall tales: 23 – 8 = 15. Or I added the other three bars: 5 + 4 + 6 = 15. Accept either method.

Teaching note: The sample graph is a teaching model; the child’s own survey totals will differ. Use the observation checklist below.

Hands-on task observation checklist (Survey: favorite kind of story or song). 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 asked exactly 10 people the survey question.
  • ☐ Child recorded tally marks and correct totals.
  • ☐ Child colored each bar to the correct height.
  • ☐ Child made a picture graph that matches the totals.
  • ☐ Child wrote and answered a compare question about the graph.

Day 85: Independent Check: Word Problems, Within 1000 and Bar Graphs

Standard: Grade 2 Math Standard 1, 2.OA.A.1; Grade 2 Math Standard 12, 2.NBT.B.12; Grade 2 Math Standard 12, 2.NBT.B.12a; Grade 2 Math Standard 16, 2.DA.A.16; Grade 2 Math Standard 16, 2.DA.A.16a

Practice figure: Bar graph: Signs of Animals Found, printed on the Week 17 Practice Workbook. Bar heights: Tracks 7, Nests 3, Holes 5, Feathers 4.

Worked example: Solve 260 + 140. Worked answer: 400.

  1. □ + 37 = 91. 54 children were there at first.
  2. 7 apples (15 + 18 = 33, then 40 – 33 = 7).
  3. 923.
  4. 462.
  5. 4 more. The tracks bar reaches 7 and the nests bar reaches 3, and 7 – 3 = 4. Accept 4 with both bar heights read from the scale.

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

Week 17 Student Textbook | Week 17 Practice Workbook | Week 17 Teacher Guide | Week 16 Student Textbook | Grade 2 index

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