Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

 

[divider] [/divider] Students are able to…

  • Use strategies to add and subtract 10 from any given number within 1-100.
  • Describe their strategy using place value patterns or a hundreds/120s chart.
  • Mentally add or subtract 10 from a given number within 1-100.

[divider] [/divider] Students are able to…because teachers:

  • Provide students with situations that require them to add or subtract 10 from a given number.  For example, I have 42 gummy bears and my friend game 10 more or there are 57 toy cars on the table and 10 rolled away.
  • Ask questions that require students to use a hundreds/120s chart to show patterns.
  • Provide games that require students to add or subtract 10 from a given number.

[divider] [/divider] Questions to ask students:

  • Can you find 67 on the hundreds chart, how would you find 10 more? 10 less?
    • Sample answer that indicates understanding: Student points to the 67 and then says, “I can move down one row and find 10 more or move one row up and find 10 less”
  • How do you know that 54 is 10 more than 44?
    • Sample answer that indicates understanding: “I know that 54 is 10 more because it has one more ten than 44.”

[divider] [/divider] Additional Resources:

Learn Zillion Video: Fluently Adding Ten to a Two-Digit Number

Learn Zillion Video: Finding Ten Less than a Number

 

[divider] [/divider] Sample Formative Assessment Tasks:

[divider] [/divider] Resources/Tasks to Help Your Child at Home:

Task: Use a deck of cards to practice counting on or back by 10. Flip over two digits to create a number.  Have your child say the number ten more and the number ten less than the given number.

 

Number Line Interactive Online Tool – Use an interactive online number line to count by tens from any given number. https://goo.gl/VHuKWy

 

Task: Use a 120s chart (https://goo.gl/NngTgc) to explore patterns. Start at the 7 and go down the column.  Ask your child, “What do you notice?”  They should notice the ones place stays the same but the tens place is increasing by one ten each time.  Then move to rows starting at 41, go across the row.  Ask your child, “What do you notice?”  They should notice the ones place is increasing by one 1 while the tens place stays the same.

 

Learn Zillion Video: Fill in the Missing Numbers in 120 Chart https://goo.gl/S8DCUo