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.
In earlier lessons, students learned to determine which number is greater or smaller than another number, when the numbers are zero through 10. They also learned to use the symbols for greater than and less than to indicate which number is bigger or smaller. In this lesson, they extend that knowledge to compare the size of numbers from 11 through 20 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. Based on that fact, students learn in this lesson that any two-digit number is greater than any one-digit number. 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.