A rectangular water tank is 90 cm wide and 40 cm deep. If it can contain 576 litres of water. What is its length?

Answer

To find the length of the rectangular water tank, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Width (W) = 90 cm
- Depth (D) = 40 cm
- Volume (V) = 576 liters

2. **Convert Volume from Liters to Milliliters:**
- Since 1 liter = 1000 milliliters, we convert 576 liters to milliliters:
\[ V = 576 \text{ liters} \times 1000 \text{ ml/liter} = 576000 \text{ ml} \]

3. **Write the Formula for Volume of a Rectangular Tank:**
- The formula for the volume of a rectangular tank is:
\[ V = L \times W \times D \]
where \( L \) is the length.

4. **Substitute the Known Values into the Volume Formula:**
- We substitute the values we know into the formula:
\[ 576000 = L \times 90 \times 40 \]

5. **Calculate the Product of Width and Depth:**
- Calculate \( 90 \times 40 \):
\[ 90 \times 40 = 3600 \]

6. **Rearrange the Equation to Solve for Length (L):**
- Now we can rearrange the equation to find \( L \):
\[ L = \frac{576000}{3600} \]

7. **Perform the Division:**
- Divide:
\[ L = 160 \text{ cm} \]

8. **Convert Length from Centimeters to Meters:**
- Since 1 meter = 100 cm, we convert 160 cm to meters:
\[ L = \frac{160}{100} = 1.6 \text{ meters} \]

### Final Answer:
The length of the tank is **1.6 meters**.