To compare foods fairly, put them on the same basis first. Convert each value to per 100 g, then compare, then write a conclusion that names the basis.
This lesson is part of nutrition and food technology. The next lesson, explaining preservation principles, uses the same comparing habit.
Which number should I compare?
Compare the number that matches the question. A question about a food itself needs per 100 g. A question about what one person takes in needs the serving size and the number of servings.
Both readings are correct. They answer different questions, which is why the same two foods can swap places.
Worked example: two biscuits
The table is from an original label, with invented values.
| Biscuit X | Biscuit Y | |
|---|---|---|
| Serving size | 30 g | 45 g |
| Sugar per serving | 12 g | 15 g |
Per serving. Y has 15 g and X has 12 g, so Y gives more sugar per serving.
Per 100 g. For X, 12 ÷ 30 × 100 = 40 g. For Y, 15 ÷ 45 × 100 = 33.3 g. Now X has more sugar in the food itself.
Written conclusion. “Per 100 g, Biscuit X has more sugar (40 g) than Biscuit Y (33.3 g). Assuming the labels are accurate, X is the sweeter food, although one serving of Y gives 3 g more sugar.”
The mistake that costs marks
The common slip is to compare the two printed numbers directly and stop. The working looks complete, but the comparison is unfair because the servings differ in mass.
| Step | Wrong | Right |
|---|---|---|
| Choose the basis | Use the printed serving values | Convert to per 100 g |
| Compare | 15 g > 12 g | 40 g > 33.3 g |
| Conclusion | Y has more sugar | X has more sugar per 100 g |
| Assumption | (none stated) | Labels are accurate |
The fix is to write the basis in the sentence every time: “per 100 g”, “per serving” or “per day”.
A conclusion you can reuse
Use one pattern for any data question: basis, comparison with numbers, assumption. For example: “Per [basis], [food A] has [more or less] [nutrient] ([value]) than [food B] ([value]), assuming [condition].”
The pattern keeps the answer short and covers what a marker looks for. The graph evidence and fair-comparison lab lets you practise the same habit on graphs.
Check yourself
Drink A has 20 g of sugar in a 250 mL can. Drink B has 24 g of sugar in a 330 mL can. Which drink has the higher sugar concentration, and which gives more sugar in one can?
Answer
Convert to per 100 mL. For A, 20 ÷ 250 × 100 = 8 g. For B, 24 ÷ 330 × 100 = 7.3 g (to one decimal place).
Drink A is more concentrated, with 8 g per 100 mL against 7.3 g. Drink B gives more sugar in one can, with 24 g against 20 g, because the can is larger.
Assumption: the labels are accurate and one whole can is drunk.
What to study next
Continue with explaining preservation principles, then test the whole cluster with the nutrition and food technology practice set.
If you want a teacher to check your written conclusions with you, see online one-to-one Science tuition.