In an earlier lesson, students learned to subtract a one-digit number from a two-digit number
In this lesson, students begin to learn how to subtract a two-digit number from a two-digit number for all two-digit numbers. The student learns to use the standard algorithm, along with a Place Value Table to represent the operations in each step. The use of the Table illustrates the fact that subtraction in each column means like units are subtracted from like units in each case – ones are subtracted from ones in the first column, and tens are subtracted from tens in the tens place.
In this lesson students learn how to subtract a two-digit number from a two-digit number for all two-digit numbers, when regrouping is not required. The subtraction is completed first on the ones place, then the tens place.
In the problems in this lesson, students subtract two-digit numbers using the standard algorithm when they have a Place Value Table present that can be used to represent the operations in each step. Students enter the digits in the answer separately and they are evaluated separately.
In this lesson students learn how to subtract a two-digit number from a two-digit number for all two-digit numbers, when regrouping is required. When the digit subtracted in the ones place is larger than the digit in the number it is subtracted from, regrouping is required. The process is the inverse of the “make a ten” strategy which requires decomposing a ten. It’s called “breaking a ten” into ten ones. The minuend is first decomposed into the sum of ten and some number of ones. The subtrahend is then subtracted from ten.
In the tens column, the digit subtracted is subtracted from the digit that was earlier decremented as a result of breaking a ten into ones. The result is the difference.
In the problems in this lesson, students subtract two-digit numbers requiring regrouping using the standard algorithm when they have a Place Value Table present that can be used to represent the operations in each step, including the process of breaking a ten into ten ones. Students enter the digits in the answer separately, as well as the results of decrementing the digit in the tens place of the minuend and each of these digits is evaluated separately.
In this lesson, students learn to subtract a two-digit number from a two-digit number requiring regrouping using the standard algorithm without the aid of a Place Value Table. Students enter the digits in the answer separately, as well as the results of decrementing the digit in the tens place of the minuend and each of these digits is evaluated separately.
In this lesson, students subtract a two-digit number from a two-digit number both with and without regrouping using the standard algorithm.
They enter only their final answer, which is evaluated in its entirety.