1800 تن بر هکتار = ؟ mg بر روی cm مربع

We know that 1 ton (metric) = 1000 kg, 1 kg = 1000 g, and 1 g = 1000 mg.

$$1 \text{ ton} = 1000 \text{ kg} \times \frac{1000 \text{ g}}{1 \text{ kg}} \times \frac{1000 \text{ mg}}{1 \text{ g}} = 10^9 \text{ mg}$$

So, 1800 tons is:

$$1800 \text{ ton} = 1800 \times 10^9 \text{ mg}$$

We know that 1 hectare = 10,000 m$^2$, and 1 m = 100 cm, so 1 m$^2$ = $(100 \text{ cm})^2 = 10,000 \text{ cm}^2$.

$$1 \text{ hectare} = 10,000 \text{ m}^2 \times \frac{10,000 \text{ cm}^2}{1 \text{ m}^2} = 10^8 \text{ cm}^2$$

Now we can substitute these conversions into the original expression:

$$\frac{1800 \text{ ton}}{1 \text{ hectare}} = \frac{1800 \times 10^9 \text{ mg}}{10^8 \text{ cm}^2}$$ $$\frac{1800 \times 10^9}{10^8} \frac{\text{mg}}{\text{cm}^2} = 1800 \times 10^{(9-8)} \frac{\text{mg}}{\text{cm}^2}$$ $$1800 \times 10^1 \frac{\text{mg}}{\text{cm}^2} = 18000 \frac{\text{mg}}{\text{cm}^2}$$

The final answer is $18000 \frac{\text{mg}}{\text{cm}^2}$.