Work through the levels in order. Type your answer and press Check — open the worked solution if you get stuck. Answers like -6, 3/4 or 0.25 are typed exactly as shown. A ⭐ Bonus Challenge at the end is extra credit — skip it if the rest was hard work.
Level 1 · Warm-up
1 In a study, scientists change the amount of fertiliser and measure how tall the plants grow. What is being measured?
Show worked solution
The height of the plants — the fertiliser is what they change.
2 From the methane table, write the amount produced with a low forage diet and no supplement, and with a low forage diet and high supplement.
Show worked solution
Down the low-forage column: 150 g with none, and 30 g with high supplement.
3 A cow produces 30 g of methane a day. How many grams does it produce in one week?
Show worked solution
30 × 7 = 210 g.
Level 2 · Core
4 To see the effect of the supplement while keeping the diet the same, which way should you read the table?
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Down a column — the diet is fixed by the column, so only the supplement changes.
5 A group of 10 cows each produce 40 g of methane a day. Write the group total for one day, and the group total for one week, both in grams.
Show worked solution
40 × 10 = 400 g a day, and 400 × 7 = 2800 g in a week.
6 In the carbon dioxide table, the low forage column reads 7600, 7800, 7700 as the supplement increases. How many of those three values are lower than the first?
Show worked solution
Both 7800 and 7700 are higher than 7600, so 0 — which is why the supplement does not always reduce carbon dioxide.
Level 3 · Challenge
7 Scientists fed cows for two weeks and measured gas only in the second week.1 Measuring in week 1 might catch cows still adjusting.
2 The design makes the results more trustworthy.
3 The main reason was to save the scientists work.
Which statements are correct?
2 The design makes the results more trustworthy.
3 The main reason was to save the scientists work.
Which statements are correct?
Show worked solution
Week 1 would catch cows adjusting (1 ✓), and waiting makes the readings trustworthy (2 ✓). Saving work is never the design reason (3 ✗). 1 and 2.
8 Each group in the study had 10 cows rather than 1. Write the number of cows in a group, and how many groups there were if 3 diets were each tested with 3 supplement amounts.
Show worked solution
Each group had 10 cows, and 3 × 3 = 9 combinations were tested, so 9 groups.
9 A group of 10 cows produces 30 g of methane per cow per day. How many grams does the group produce over two weeks?
Show worked solution
30 × 10 = 300 g a day, and 300 × 14 = 4200 g.