1. An estimate checks the scale
Eight fictional items cost R19 each. Round R19 to about R20 for a quick rough calculation.
Estimate: 8 × R20 ≈ R160.
Exact product of the stated values: 8 × R19 = R152.
The estimate is R8 above that exact product. It helps you notice a large input error, but is not a verified amount to pay. State the units, assumptions and whether your result is approximate.
Try it: Choose a different safe quantity and price. Predict a rounded total, calculate the exact product and explain the difference.
2. Read the row and the column
| Item | Quantity (items) |
|---|---|
| Notebooks | 6 |
| Folders | 10 |
| Markers | 8 |
| Total | 24 |
6 + 10 + 8 = 24 items.
Folders are the largest category in this table. The total row summarises the three item rows; adding the total to those rows again would double-count. This count says nothing about other cupboards. A blank cell would need clarification rather than an automatic zero.
Try it: Write a question that needs one cell, then a different question that needs a calculation.
3. Read the labelled scale
| Day | Visits |
|---|---|
| Monday | 6 |
| Tuesday | 10 |
| Wednesday | 8 |
Tuesday has the largest displayed count. The chart alone does not explain why. Visits are not automatically unique visitors, purchases or satisfied customers.
Try it: Calculate Tuesday minus Monday, then state a conclusion the chart does not support.
4. Define the whole before its fraction
One quarter: 16 ÷ 4 = 4.
Three quarters: 3 × 4 = 12 counters.
All sixteen squares are equal-sized. Twelve are marked with a tick as well as colour. The fraction is relative to this whole; three quarters of a different total can be a different number.
Try it: Draw another whole divided into equal parts and explain its marked share.
5. A ratio compares labelled quantities
| Part | Ratio units | Counters |
|---|---|---|
| Blue | 1 | 6 |
| Gold | 2 | 12 |
| Total | 3 | 18 |
1 + 2 = 3 ratio units.
18 ÷ 3 = 6 counters per ratio unit.
Blue: 1 × 6 = 6. Gold: 2 × 6 = 12.
Check: 6 + 12 = 18, and 6:12 simplifies to 1:2.
Blue is one third of the whole, not one half: the ratio 1:2 is part-to-part, while the whole has three ratio units.
Try it: Keep the same ratio and use a different divisible total. Check both the sum and relationship.
6. Compare on the same basis
| Offer | Items | Pack price | Price per item |
|---|---|---|---|
| A | 6 | R27 | R4.50 |
| B | 10 | R40 | R4.00 |
A: R27 ÷ 6 = R4.50 per item.
B: R40 ÷ 10 = R4.00 per item.
B has the lower stated unit price, while A has the lower pack price. Which matters depends on the actual need and conditions. Check item equivalence, exclusions, affordability and whether the quantity is useful. These figures alone do not establish overall quality or a best choice for everyone.
Try it: Add a fictional delivery cost and recalculate the comparable totals.