Although column subtraction is specified for Year 3 in the National Curriculum, Hamilton believe that teaching column subtraction in Year 4 will be more successful. The National Curriculum Guidance specifies that teachers can teach areas of study in different year groups than those mentioned in the Curriculum, so long as they are taught within the same Key Stage. If you would like to teach column subtraction in Year 3 please see Year 4 Addition and Subtraction autumn Unit 7, spring Unit 4 and summer Units 2 and 3.
Day 1 Teaching
Show items for sale (see resources). Children remove 10p from each price and show you on whiteboard. Then start again and remove 9p from each price. Practise reducing by other amounts, e.g. 12p, 21p, etc. Use Spider on the 1-100 grid to demonstrate.
-- Reduce prices by near multiples of 10p.
Use Maths Frog. He helps us to subtract by counting up to find a difference. He ALWAYS hops to the next 10 and then to 100. He starts with the smaller number. Write notes. Use Frog for 45 – 32, 78 – 44, 54 – 23. Model: Below the line record the numbers where Frog lands and above the line the size of each hop.
Use the ‘Magic square differences’ in-depth problem-solving investigation below as today’s group activity.
Or, use these activities:
-- Choose numbers between given multiples of 10, use Frog to subtract the smaller from the larger aiming to find the smallest and biggest answers that they can. Use landmarked lines.
-- Use Frog to work out how much dogs have grown. Draft own number line jottings.
We’ve revised different ways of subtracting; we’ve looked at using Frog to count up and counting back to subtract near multiples. Write: Frog and Counting Back as column headings. Ask children to give an example for each. Correct misunderstandings.
-- Choose Frog or Counting Back to subtract.