Solve Problems with Many Operations

10 min

Narrative

The purpose of this True or False is to elicit strategies and understandings students have for finding differences between two numbers. These understandings help students build fluency in addition and subtraction, while preparing them to think about distances between two points.

Students may use estimation or place value understanding to solve the problems (MP7).

Launch

  • Display one statement.
  • “Give me a signal when you know whether the statement is true and can explain how you know.”
Teacher Instructions
  • 1 minute: quiet think time
  • Share and record answers and strategy.
  • Repeat with each statement.

Student Task

Decide if each statement is true or false. Be prepared to explain your reasoning.

  • 50,000−999=49,00150,000 - 999 = 49,001
  • 4,799=5,000−3114,799 = 5,000 - 311
  • 3,005=4,000−1,9953,005 = 4,000 -1,995
  • 2,000−1,234=1,8762,000 - 1,234 = 1,876

Sample Response

  • True: 49,001+999=50,00049,001 + 999 = 50,000.
  • False: 4,800 is 200 from 5,000, so 4,799 is 200+1200 + 1 or 201 from 5,000.
  • False: 3,000 is 4,000−1,0004,000 - 1,000, so 3,005 is just 5 less than 1,000 from 4,000. (It cannot be almost 2,000 away from 4,000.)
  • False: 2,000−1,2002,000 -1,200 is 800, so 2,000−1,2342,000 - 1,234 is a little less than 800 (instead of 1,000 more than 800).
Activity Synthesis (Teacher Notes)
  • “How can we tell if each equation is true without calculating?”
  • “We could use the standard algorithm to find each difference and then decide if the equation is true or false. Would that be a good idea? Why or why not?”
Standards
Addressing
  • 4.NBT.4·Fluently add and subtract multi-digit whole numbers using the standard algorithm.
  • 4.NBT.B.4·Fluently add and subtract multi-digit whole numbers using the standard algorithm.

20 min

15 min