题目内容
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We have tested a plant's emissions of particulates and found the following data:
| Sample number | Stack velocity, ft/s | Particle concentration, g/m3 |
| 1 2 3 | 50 60 40 | 0.50 0.30 0.70 |
Each sample represents the average over a 20-min period. What was the average particle concentration in this stack over the whole 60 min of this test？
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