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
Write 137 – 72. Agree we can use Frog to find this difference, by, counting up from 72 to 137. Draw an empty number line jotting to show this and model each of Frog’s jumps (72 to 80, 80 to 100 and 100 to 137). Explain that we can do 1 big jump to 100. Repeat to model using Frog to do £1.46 – 83p. Children try £1.23 – 88p.
-- Use Frog to calculate the amount left in a purse after buying an item.
-- Use Frog to calculate differences.
Day 2 Teaching
Display a word problem resulting in the calculation 476 – 438. How can Maths Frog help us to work this out? Frog will start on 438, jump to the next 10 (440), then jump to 470, then 476. Remind children that we could do one big jump of 36 from 440 to 476 if we are confident but we don’t have to! Children try 873 – 837.
-- Investigate reversing the last 2 digits of a 3-digit number, then use Frog to find the difference between them.
Day 3 Teaching
Show a toy priced £4.67. Give a child a £5 note and ask them to use this to pay for the toy. You’ve given the shopkeeper too much money. How will she work out how much change to give you? Maths Frog can help us! Sketch a line from £4.67 to £5. Model using Frog to hop to £4.70 and then to £5. Repeat, to find change from £10 and £20.
Use the ‘Step Change’ in-depth problem-solving investigation below as today’s group activity.
Or, use these activities:
-- Practise finding the change from £5, £10 and £20.
-- Play online checkout/ change games, finding change from £1, £5 and £10.
Day 4 Teaching
Show a game and say that it costs £18. So far Katie has saved up £7.55. How much more does she need? Maths Frog can help! Sketch a line from £7.55 to £18. Model the hops from £7.55 to £7.60, then to £8, then to £18. Ensure children add hops accurately to find the answer: £10.45. Repeat as necessary for finding the difference between £8.43 and £14, then £6.55 and £19.
-- Calculate how much more money is needed to pay for a range of items.
-- Calculate how much more money is needed to pay for a more expensive version of an item.
Day 5 Teaching
A family have £100 and so far have spent £67.73. How much money is left? Use Frog to model the hops. Ask children to add the jumps, adding the £s first then the pence, then put them together. Some children may draw 3 hops, others draw 4. It doesn’t matter as long as we get the right answer! Repeat for a family who have spent £62.41 out of their £100.
-- Practise finding change from £100 (or £20) for a range of items.
-- Play ‘Change from £100’ pairs, ‘Change from £20’ pairs.