S: 22,397 minus 3,745 equals 18,652. T: Check your answer using addition. S: Our answer is correct because 18,652 plus 3,745 equals 22,397. T: What is the value of A in the tape diagram? S: A equals 18,652. Problem 2: Subtract, decomposing three times. Write 210,290 – 45,720 vertically on the board. T: With your partner, draw a tape diagram to represent the whole, the known part, and the unknown part. T: Record the subtraction problem on your board. T: Look across the digits. Are we ready to subtract? S: No! T: Look across the top number’s digits to see if we have enough units in each column. Are there enough ones in the top number to subtract the ones in the bottom number? (Point to the zeros in the ones column.) S: Yes, 0 equals 0. T: We are ready to subtract in the ones column. Are there enough tens in the top number to subtract the tens in the bottom number? S: Yes, 9 is greater than 2. T: We are ready to subtract in the tens column. Are there enough hundreds in the top number to subtract the hundreds in the bottom number? S: No, 2 hundreds is less than 7 hundreds. T: There are no thousands to unbundle, so we look to the ten thousands. We can unbundle 1 ten thousand to 10 thousands. Unbundle 10 thousands to make 9 thousands and 12 hundreds. Now we can subtract the hundreds column. Repeat questioning for the thousands, ten thousands, and hundred thousands place, recording the renaming of units in the problem. T: Are we ready to subtract? S: Yes, we’re ready to subtract! T: 0 ones minus 0 ones? S: 0 ones. T: 9 tens minus 2 tens? S: 7 tens. Have partners continue using the algorithm, reminding them to work right to left, always naming the units. T: Read the equation to your partner and complete your tape diagram by labeling the variable. S: 210,290 minus 45,720 is 164,570. (A = 164,570.) Problem 3: Use the subtraction algorithm to solve a word problem, modeled with a tape diagram,
S: 22,397 minus 3,745 equals 18,652. T: Check your answer using addition. S: Our answer is correct because 18,652 plus 3,745 equals 22,397. T: What is the value of A in the tape diagram? S: A equals 18,652. Problem 2: Subtract, decomposing three times. Write 210,290 – 45,720 vertically on the board. T: With your partner, draw a tape diagram to represent the whole, the known part, and the unknown part. T: Record the subtraction problem on your board. T: Look across the digits. Are we ready to subtract? S: No! T: Look across the top number’s digits to see if we have enough units in each column. Are there enough ones in the top number to subtract the ones in the bottom number? (Point to the zeros in the ones column.) S: Yes, 0 equals 0. T: We are ready to subtract in the ones column. Are there enough tens in the top number to subtract the tens in the bottom number? S: Yes, 9 is greater than 2. T: We are ready to subtract in the tens column. Are there enough hundreds in the top number to subtract the hundreds in the bottom number? S: No, 2 hundreds is less than 7 hundreds. T: There are no thousands to unbundle, so we look to the ten thousands. We can unbundle 1 ten thousand to 10 thousands. Unbundle 10 thousands to make 9 thousands and 12 hundreds. Now we can subtract the hundreds column. Repeat questioning for the thousands, ten thousands, and hundred thousands place, recording the renaming of units in the problem. T: Are we ready to subtract? S: Yes, we’re ready to subtract! T: 0 ones minus 0 ones? S: 0 ones. T: 9 tens minus 2 tens? S: 7 tens. Have partners continue using the algorithm, reminding them to work right to left, always naming the units. T: Read the equation to your partner and complete your tape diagram by labeling the variable. S: 210,290 minus 45,720 is 164,570. (A = 164,570.) Problem 3: Use the subtraction algorithm to solve a word problem, modeled with a tape diagram,