Solve the following subtraction problems using the vertical form method. Explain the steps involved in subtracting 45 - 27.

Here is the blackboard plan, just like the sample in the picture:

Sample Blackboard Plan

Date: (Leave blank) Chapter: Addition and Subtraction Topic: What we learned at Elementary Lesson: of 15

Let's think about subtracting vertically.

34 Find answers in vertical form.

1. $76 - 32$
2. $56 - 40$
3. $58 - 5$
4. $98 - 18$
5. $43 - 42$
6. $30 - 20$

35 Explain subtraction in vertical form.

How to Subtract $45 - 27$ Using Vertical Form

• Step 1: Line up numbers in each column. $$\begin{array}{c} 45 \\ -27 \\ \hline \end{array}$$
• Step 2: Borrow 1 ten as 10 ones.
  • $10 + 5 = 15$ ones.
  • $15 - 7 = 8$.
  • The ones place of the answer becomes $\boxed{8}$.
  $$\begin{array}{c} \phantom{0}\overset{3}{\cancel{4}}\overset{10}{\cancel{5}} \\ -27 \\ \hline \phantom{0}8 \\ \end{array}$$
• Step 3: Subtract the tens.
  • 1 ten has been borrowed by the ones place.
  • So $3 - 2 = \boxed{1}$.
  $$\begin{array}{c} \phantom{0}\overset{3}{\cancel{4}}\overset{10}{\cancel{5}} \\ -27 \\ \hline \phantom{0}18 \\ \end{array}$$

Visual Explanation (MT)

• Initial number 45:
  • Tens Place: 4 vertical blocks (representing 40)
  • Ones Place: 5 small horizontal blocks (representing 5)
• Borrow 1 ten as 10 ones:
  • Tens Place: 3 vertical blocks (representing 30)
  • Ones Place: 15 small horizontal blocks (representing 15). An arrow shows one vertical block moving from tens to ones and changing into 10 small horizontal blocks.
• Subtracting 27:
  • Tens Place: 3 vertical blocks, with 2 crossed out (representing $3-2=1$).
  • Ones Place: 15 small horizontal blocks, with 7 crossed out (representing $15-7=8$).
• Result:
  • Tens Place: 1 vertical block (representing 10)
  • Ones Place: 8 small horizontal blocks (representing 8)

36 Find answers in vertical form.

1. $41 - 19$
2. $70 - 56$
3. $26 - 18$
4. $90 - 88$
5. $92 - 8$
6. $40 - 7$

Homework