Subtraction Notes, Quizzes & Revision

Subtraction is the operation of taking away one number from another. It answers questions such as "How many are left?" or "What is the difference?" In real life: giving change in KSh, sharing fruit, or comparing amounts.

• Subtract / take away / minus
• Difference — result of subtraction
• Minuend — the number we start with (what we take from)
• Subtrahend — the number we subtract
• Regrouping / borrowing — when we take from the next place value

1. Take-away model — remove objects from a collection.
   🍎🍎🍎🍎🍎 Take away 2 → 🍎🍎 (3 left)
2. Comparison model — find how much more one amount is than another.
   Example: Amina has 18 beads, John has 13. Difference = 18 − 13 = 5
3. Missing-addend model — find the number you add to the smaller to get the larger.
   Find x: 14 − x = 6 → x = 8 because 6 + 8 = 14

Start at the minuend and jump back by the subtrahend.

Example: 9 − 4. Start at 9, jump back 4 steps to land on 5 → answer 5.

Put numbers in place-value columns (units under units, tens under tens).

Work from right (units) to left (tens). 3 − 4 cannot take; but here 3 >= 4? No, so we learn regrouping next.

When the digit on top is smaller than the digit below, borrow 1 from the next left place (10 units = 1 ten).

Explanation: 59 − 27: borrow 1 ten from 5 → tens become 4 (shown as 5 but unit 9 is after borrowing in method) then units: 19 − 7 = 12 (write 2 carry 1 to tens) then tens: 4 − 2 + carried 1 = 3 → result 32. (Teachers may show clearer step-by-step with marks for the borrow.)

1. Ms. Wanjiru had 120 KSh. She bought maize that cost 45 KSh. How much money is left?
   120 − 45 = 75 KSh
2. There were 36 mangoes on a tree. Birds ate 8 mangoes. How many remain?
   36 − 8 = 28 mangoes
3. Sali had 204 shillings. He spent 159 shillings. What was left?
   204 − 159 = 45 KSh

• Not lining up digits by place value — always put units under units, tens under tens.
• Forgetting to borrow when needed — check units first, then tens.
• Mixing up subtraction direction — minuend − subtrahend; if unsure, use the number line or ask "how many more to make the bigger number?"
• Check answer by adding: (result + subtrahend) should equal minuend.

1. 45 − 17 = ?
2. 82 − 39 = ?
3. 150 − 76 = ?
4. 67 − 28 = ?
5. 200 − 158 = ?

Ask a learner: "If you have 90 KSh and spend 37 KSh, how much is left? Show using counters and the column method." Look for correct alignment and borrowing where needed.

Work with three-digit subtraction and practice subtraction where we subtract a larger number from a smaller one by introducing negative results (for older learners) or by using the missing-addend model instead.