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Grade 2 Mathematics Week 9 | Student Textbook

Grade 2 | MATHEMATICS

WEEK 9 • STUDENT TEXTBOOK • DAYS 41–45

Read each lesson with a parent or teacher and study the worked example. Then answer the questions for that day in the Week 9 Practice Workbook.

Week 9 Student Textbook | Week 9 Practice Workbook | Week 9 Teacher Guide | Week 8 Student Textbook | Week 10 Student Textbook | Grade 2 index

Day 41: Estimate Lengths

To estimate is to make a careful guess. You can estimate with things you know: a large paper clip is about 1 inch long, a fingertip is about 1 centimeter wide, and a big step is about 1 meter.

After you estimate, measure to check. Good estimators get closer each time they practice.

Worked example: A stapler is about as long as 6 large paper clips in a row. Estimate its length in inches.

  1. Each large paper clip is about 1 inch.
  2. 6 paper clips are about 6 inches.

Worked answer: About 6 inches.

Day 42: How Much Longer?

To find how much longer one object is than another, measure both in the same unit. Then subtract the shorter length from the longer length.

You can also count up from the shorter length to the longer length. Both ways give the difference.

Worked example: A blue ribbon is 14 inches long. A red ribbon is 9 inches long. How much longer is the blue ribbon?

  1. Both are measured in inches.
  2. Subtract: 14 – 9 = 5.
  3. Or count up from 9 to 14: 5 inches.

Worked answer: The blue ribbon is 5 inches longer.

Day 43: Length Word Problems

Some word problems are about lengths. Read carefully to decide whether to add or subtract. Keep the same unit all the way through.

Draw a quick picture, such as two bars, to show the lengths. Write an equation with a box or a question mark for the unknown.

Worked example: A path is 45 feet long. Workers add 28 more feet. How long is the path now?

  1. The path gets longer, so add.
  2. 45 + 28 = ?
  3. 40 + 20 = 60 and 5 + 8 = 13. 60 + 13 = 73.

Worked answer: The path is 73 feet long.

Day 44: Lengths on a Number Line

A number line is like a ruler. The numbers are equally spaced, starting at 0. Each number tells a length from 0.

To add on a number line, start at the first number and jump forward. To subtract, start at the first number and jump back. You can make jumps of 10 and then jumps of 1.

Worked example: Use a number line to find 36 + 25.

  1. Start at 36.
  2. Jump 10 to 46, then 10 to 56.
  3. Jump 5 more to 61.

Worked answer: 36 + 25 = 61.

Day 45: Independent Check: Estimate, Compare and Solve

Today you will answer on your own.

Use what you learned this week: estimate with things you know, compare lengths in the same unit, draw a picture for word problems, and use a number line.

Worked example: A green crayon is 9 centimeters and a red crayon is 7 centimeters. How much longer is the green crayon?

  1. Same unit: centimeters.
  2. 9 – 7 = 2.

Worked answer: 2 centimeters longer.

Week 9 Student Textbook | Week 9 Practice Workbook | Week 9 Teacher Guide | Week 8 Student Textbook | Week 10 Student Textbook | Grade 2 index