How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Opening stock: 100 units at R50. Purchases: 200 units at R55, then 150 units at R60. 120 units are on hand at year end. Use FIFO to calculate closing stock and cost of sales.
Before any working — hunt first
Given
Numbers and units already in the sentence: 100 units · R50 · 200 units · R55 · 150 units · R60 · 120 units. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: closing stock and cost of sales. Circle that word — that is the missing variable.
Find
We are required to find: closing stock and cost of sales. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
Write 5 000 + 11 000 + 9 000 = 25 000 with empty letters. Cross out every letter that already has a number. Calculate the letter that is still standing — that gives closing stock and cost of sales.
In other words — as if you have never seen this before
If you have never seen this before: FIFO: the oldest stock is sold first, so the units left over are the most recent ones. We will name a method in words, write the formula with no numbers, then substitute one line at a time.
2. What do we already know?
100 × R50, 200 × R55, 150 × R60. Closing 120 units.
3. Which method — and why this one?
FIFO: the oldest stock is sold first, so the units left over are the most recent ones.
4. Step-by-step working
01 / 06
Calculate
Total cost of goods available = 5 000 + 11 000 + 9 000 = R25 000 (450 units).
5 000+11 000+9 000=25 000Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
02 / 06
Multiply
Closing stock = the last 120 units bought = 120 × R60 = R7 200.
120×60=7 200Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
03 / 06
Subtract
Cost of sales = 25 000 − 7 200 = R17 800.
25 000−7 200=17 800Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
04 / 06
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
05 / 06
Step F — Box the answer with its unit
Closing stock R7 200; cost of sales R17 800.
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
06 / 06
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
Closing stock R7 200; cost of sales R17 800.
Copy onto your answer sheet — in this order
Formula: 5 000+11 000+9 000=25 000
Answer: Closing stock R7 200; cost of sales R17 800.
6. Check it like a marker
Check: 330 units sold=100×50+200×55+30×60=5 000+11 000+1 800=R17 800.
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”