An investigation was carried out to measure the rate of transpiration in four different plant species under controlled, warm and dry environmental conditions.
The results are shown in Table 1.
Table 1
| Plant species | Rate of transpiration (mg dm−2h−1\text{mg dm}^{-2}\text{h}^{-1}mg dm−2h−1) |
|---|---|
| Helianthus annuus (Sunflower) | 582 |
| Betula pendula (Silver birch) | 324 |
| Ammophila arenaria (Marram grass) | 168 |
| Yucca flaccida (Weak-leaf yucca) | 45 |
Calculate how many times greater the rate of transpiration of Helianthus annuus is than the rate of transpiration of Ammophila arenaria.
Give your answer to 2 significant figures.