1. **State the problem:** Ali has a cylindrical fish tank with height $80$ cm and diameter $40$ cm. We need to find the amount of salt in grams required using the formula: $$\text{Amount of salt} = \left(\frac{\text{volume of tank}}{1000}\right) \times 35$$ and check if it is more than $3750$ grams (3.75 kilograms). 2. **Calculate the volume of the cylinder:** The volume $V$ of a cylinder is given by: $$V = \pi r^2 h$$ where $r$ is the radius and $h$ is the height. Given diameter $= 40$ cm, radius $r = \frac{40}{2} = 20$ cm. Height $h = 80$ cm. Substitute values: $$V = 3.14 \times 20^2 \times 80$$ $$V = 3.14 \times 400 \times 80$$ $$V = 3.14 \times 32000$$ $$V = 100480 \text{ cubic centimeters}$$ 3. **Convert volume to liters:** Since $1000$ cubic centimeters = $1$ liter, $$\frac{100480}{1000} = 100.48 \text{ liters}$$ 4. **Calculate amount of salt:** Using the formula: $$\text{Salt} = 100.48 \times 35 = 3516.8 \text{ grams}$$ 5. **Compare with 3750 grams:** $$3516.8 < 3750$$ So, Ali's estimate that the tank needs more than 3.75 kilograms of salt is **incorrect**. **Final answer:** Ali is not correct; the tank needs approximately $3517$ grams of salt, which is less than $3750$ grams.