### Planning and Activities

**Day 1**Model expanded and compact column addition. Y3 practise adding two 3-digit numbers; Y4 add two 4-digit numbers.

**Group Activities: T with Y3**

Y3 -- Add two 3-digit numbers, using expanded and/or compact addition.

-- Make two 3-digit numbers using dice; add the numbers using compact addition.

Y4 -- Use the digits 6, 7, 8 and 9 (or 3, 4, 5 and 6) to make a 4-digit number. Reverse the digits and find the total, e.g. 7689 + 9867. Find the digit sum of the answer. Describe patterns.

**Day 2**Estimate totals by rounding to the nearest 100 or the nearest 10 before solving 3-digit additions.

**Further Teaching with Y4**

Revise compact decomposition for subtracting 3-digit numbers.

**Group Activities: T with Y4**

Y3 -- Think mathematically to use chosen digits to make two (or three) 3-digit numbers with a total as close as possible to 600 (or 1000). Use compact addition.

-- Estimate the total of two 3-digit numbers; find the exact total using compact addition.

Y4 – Work towards securing a written method for 3-digit subtractions.

– Consolidate use of compact column subtraction. Consider the most appropriate/efficient method for subtraction.

**Day 3**Discuss why and where there will be ‘carries’ in 3-digit additions.

**Further Teaching with Y4**

Model compact decomposition of 4-digit numbers. Discuss why and where there will be ‘moves’ across columns in 4-digit subtractions.

**Group Activities: T with Y4**

Y3 -- Investigate addition of pairs of palindromic numbers.

Y4 – Use base-10 equipment in a place value grid to help with expanded column subtraction of 4-digit numbers (1 move).

– Begin to use compact column subtraction of 4-digit numbers (1 move).

**Day 4**Model addition of several 2-digit numbers using column addition.

**Further Teaching with Y4**

Further use of decomposition to subtract 4-digit numbers: 2 moves across columns.

**Group Activities: T with Y3**

Y3 -- Add three or four 2-digit numbers, using expanded and compact addition.

-- Estimate the total when adding three or four 2-digit numbers, then find the answer using compact addition.

Y4 -- Begin to secure use of expanded column subtraction to subtract pairs of 4-digit numbers.

-- Secure use of expanded column subtraction to subtract pairs of 4-digit numbers; begin to use compact subtraction. Subtract amounts of money.

**Day 5**Consider mental strategies to solve 300 – 256, 678 – 523 and 678 – 199.

**Further Teaching with Y3**

Estimate and add three or four 2-digit numbers using expanded or compact addition.

**Group Activities: T with Y3**

Y3 -- Add several 2-digit numbers with a given target total.

Y4

*Use the in-depth problem-solving investigation ‘Subtraction Surprise’ from NRICH as today’s group activity.*

Or, use this activity:

-- Create subtraction questions that can be solved mentally.