Split and join: 4-digit sums — Speed Calculation

The fast method

Split and join — “cut each number into two 2-digit halves, work them separately, fix the join”

1. Split each 4-digit number into two 2-digit halves: 4768 → 47|68.
2. Work out the left halves and the right halves on their own.
3. Adding: a right half of 100 or more carries 1 to the left half.
4. Subtracting: right half too small? Borrow 1 from the left half — it is worth 100 on the right.

Use it for: Bills and budgets, adding marks or distances, year gaps in history, and long sums in Class 5–8 without paper.

Worked example: 4768 + 3657 = 8425

✏️ Practice

Work it out in your head or on paper, then tap your answer — or type it and press Check. Stuck? Press “Show me how”.

🏁 Lesson 16 test

20 questions. Check each answer, then go to the next one. Get 16 or more right to pass — and beat the clock: finish within 4 min.

🏅 Sign in with Google to earn the 🧩 Split-Join Star badge when you pass — and a certificate when you finish all 10 lessons of Part 4 · Speed decimals, fractions and percentages. You can still take the test without signing in.

🖨️ 4-Digit Mental Addition and Subtraction Worksheet

• Worksheet set 1 (PDF)
• Worksheet set 2 (PDF)
• Worksheet set 3 (PDF)