During Unit 3, your child will build critical knowledge in the understanding of the base-ten numeration system and place-value concepts.  This includes ideas of counting in units of fives, tens and multiples of hundreds, tens and ones as well as a grasp of number relationships, which they will demonstrate in a variety of ways, including comparing and ordering numbers.  They will work to understand multi-digit numbers in terms of place-value recognizing that place-value notation is shorthand for representing amounts of hundreds, tens and ones.

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Key Vocabulary

Students need to:

  • Understand that the three digits of a three-digit number represent amounts of hundreds, tens, and ones; e.g., 706 equals 7 hundreds, 0 tens, and 6 ones. Understand the following as special cases
    • 100 can be thought of as a bundle of ten tens — called a “hundred."
    • The numbers 100, 200, 300, 400, 500, 600, 700, 800, 900 refer to one, two, three, four, five, six, seven, eight, or nine hundreds (and 0 tens and 0 ones).
  • Read and write numbers to 1000 using base-ten numerals, number names, and expanded form.
  • Compare two three-digit numbers based on meanings of the hundreds, tens, and ones digits, using >, =, and < symbols to record the results of comparisons.
  • Count within 1000; skip-count by 5s, 10s, and 100s.
  • Solve word problems involving dollar bills, quarters, dimes, nickels, and pennies, using $ and ¢ symbols appropriately. Example: If you have 2 dimes and 3 pennies, how many cents do you have?
  • Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.
  • Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
  • Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem.
  • Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.