Grade 1 Math: Numbers 21-100, Part 2

In prior lessons, numbers made up of tens and ones are represented using ten frames. In this lesson, a new format is introduced – the Place Value Table. In the Place Value Table, there is a box for each place value. Each unit in a number is represented as a box in the ones place. Each ten in a number is represented as a single block in the tens place of the table.

Counting with Place Value 21-100

In this lesson, two-digit numbers are represented using the Place Value Table. Given a number represented in the Place Value Table, students write the number in three formats:

  1. the number of units and tens represented,
  2. expanded notation, and
  3. standard notation.

Expanded Forms 21-100

In this lesson, students learn to write numbers from 21 through 100 given in words as the number of tens and ones. The descriptions of the numbers are given in mixed order rather than the order of the place values in the number. Thus, the student must interpret the meaning of the place values and the number for each place value rather than just writing the numbers in the order given.

Counting: 1 or 2 more or less 21-100

In this lesson, students learn to determine what number is 1 or 2 more or less than another given number, when the number given is 11 through 20. Special emphasis is given to numbers that result in a change from a lower decade to a higher decade or from a higher decade to a lower decade.

Comparing Numbers 21-100

In earlier lessons, students learned to determine which number is greater or smaller than another number, when the numbers are 11 through 20. In this lesson, they extend that knowledge to compare the size of numbers from 21 through 100 using the symbols for greater than and less than.

Earlier they learned that a larger number is greater than another number if it comes after that number in the counting sequence. When two, two-digit numbers are compared and the first digit, in the tens place, is the same for both numbers, the comparison must be based on the second number, which is in the ones place.

In the problems in this lesson, they are given two numbers and must indicate which number is larger or smaller. They answer by writing the appropriate symbol.

Make Numbers from Digits: 2 digits

In this lesson, students extend what they know about place value concepts to write numbers from digits. They are given two digits and are to write either the largest number possible or the smallest number possible from those digits.

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