Column Subtraction Or Subtraction With Regrouping

Objectives

To understand column subtraction, recognising the need to regroup numbers, if the bottom digit is greater than the top digit.

To understand and apply the concept of place value.

Resources

Abacus 4 Textbook 1 | Squared paper | Counters or beads | Compact Column Subtraction (YouTube)

Today's Lesson

Main Activity

Further to the previous lessons, turn to page 47 in Abacus 4 Textbook 1.

This is still working on subtraction with regrouping. However, today, ask your student to attempt to copy and complete the calculations without writing them out in the expanded method: using ‘compact’ column subtraction. Watch Compact Column Subtraction (YouTube) to understand the compact method; the calculations are exactly the same, but the place of each digit will indicate its value.

For Example: Question 1:


	100s	10s	1s
	78	122	7
-	________5	_______6	_______3
	2	6	4

If your student still prefers to use the expanded method for column subtraction, this is fine. You could model the com

pact method and your student can write the more ‘place value explicit’ expanded calculation alongside. Discuss the two calculations and try to see the links between the two, e.g. how your twelve 10s are the same as the 120 in your student's calculation. Once again, representing with place value counters might be helpful.

Look at the picture problems at the bottom of the page and ask your student to say aloud what number sentence is required to solve each problem. Once this is understood, encourage your student to work independently to find an answer to each.

Citations

[1] www.youtube.com [2] www.youtube.com