Grade 2 | MATHEMATICS
WEEK 17 • STUDENT TEXTBOOK • DAYS 81–85
Read each lesson with a parent or teacher and study the worked example. Then answer the questions for that day in the Week 17 Practice Workbook.
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
In a word problem, one number is unknown. It might be the result, the change or the start. Draw a picture or a bar model to show the parts and the whole, then write an equation with a box for the unknown.
Ask: Do I know the whole, or only the parts? If you know both parts, add to find the whole. If you know the whole and one part, subtract to find the other part.
Worked example: A nursery had 34 apple trees. Some more were planted. Now there are 61. How many were planted?
- Write an equation: 34 + □ = 61.
- Think 61 – 34 = 27.
Worked answer: 27 trees were planted.
Day 82: Two-Step Word Problems
A two-step problem needs two steps of thinking. Solve the first step, then use that answer in the second step. Write each step as its own equation.
Read the whole problem first. Ask: What happened first? What happened next? What does the question ask?
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?
- Step 1: Feet laid in all: 20 + 15 = 35.
- Step 2: Feet still needed: 60 – 35 = 25.
Worked answer: 25 more feet.
Day 83: Add and Subtract Within 1000
To add or subtract three-digit numbers, line up the hundreds, tens and ones. Work one place at a time, starting with the ones.
When adding, if a place has 10 or more, trade 10 ones for 1 ten or 10 tens for 1 hundred. When subtracting, if there are not enough to take away, trade 1 ten for 10 ones or 1 hundred for 10 tens. Check a subtraction answer by adding.
Worked example: Solve 325 + 148.
- Ones: 5 + 8 = 13. Write 3 and trade 10 ones for 1 ten.
- Tens: 2 + 4 + 1 = 7. Hundreds: 3 + 1 = 4.
Worked answer: 473.
Day 84: Make and Read a Bar Graph
A survey asks people a question and records their answers. A bar graph shows the answers. The height of each bar shows how many people chose that answer. Read the number on the scale at the top of each bar.
You can use a bar graph to solve problems. Put two bars together to find how many in all. Take one bar away from the total to find how many are left. Compare two bars to find how many more or how many fewer.
Worked example: A bar graph shows 9 people chose apples and 4 chose pears. How many more chose apples?
- Read both bars: 9 and 4.
- Subtract to compare: 9 – 4 = 5.
Worked answer: 5 more people.
Day 85: Independent Check: Word Problems, Within 1000 and Bar Graphs
Today you will answer on your own.
Use what you learned this week: word problems with an unknown, two-step problems, adding and subtracting within 1000, and bar graphs.
Worked example: Solve 260 + 140.
- Tens: 6 + 4 = 10 tens. Trade for 1 hundred.
- Hundreds: 2 + 1 + 1 = 4.
Worked answer: 400.
Week 17 Student Textbook | Week 17 Practice Workbook | Week 17 Teacher Guide | Week 16 Student Textbook | Grade 2 index
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