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Missing tadpole count calculation
Table 1 shows the results.
| Sample number | 0 weeks | 1 week | 2 weeks | 3 weeks | 5 weeks | 8 weeks |
|---|---|---|---|---|---|---|
| 1 | 11 | 17 | 8 | 9 | 5 | 0 |
| 2 | 15 | 11 | 12 | 7 | 0 | 5 |
| 3 | 23 | 16 | 14 | 10 | 7 | 3 |
| 4 | 11 | 14 | 16 | X | 4 | 4 |
| Totals | 60 | 58 | 50 | 32 | 16 | 12 |
Value X is the number of tadpoles in sample 4, at 3 weeks. Calculate value X.
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Marking points
- 1 Calculates X as 6.
Full-mark answer
X = 32 − (9 + 7 + 10) = 6.
Why this answer loses marks
Subtract just one sample from the total.
The method must combine every known sample before subtracting from the total.