A rectangular water reservoir contains 126 kilolitres of water. The depth of the reservoir is 3.5 m and its length measures 8 m. What is the width of the reservoir?

Options

A. 4.5 m
B. 4.2 m
C. 4 m
D. 5 m

Answer

To find the width of the rectangular water reservoir, we can follow these steps:

### Step 1: Convert Kilolitres to Cubic Meters
We know that 1 kilolitre (kL) is equivalent to 1 cubic meter (m³). Therefore, we can convert the volume of the reservoir from kilolitres to cubic meters.

\[ \text{Volume} = 126 \text{ kL} = 126 \text{ m}^3 \]

**Hint:** Remember that 1 kL = 1 m³ for conversions.

### Step 2: Use the Volume Formula for a Rectangular Prism
The volume \( V \) of a rectangular prism (like our reservoir) can be calculated using the formula:

\[ V = \text{length} \times \text{width} \times \text{depth} \]

In our case, we have:
- Volume \( V = 126 \text{ m}^3 \)
- Length \( L = 8 \text{ m} \)
- Depth \( D = 3.5 \text{ m} \)

### Step 3: Rearrange the Formula to Find Width
We need to find the width \( W \). Rearranging the volume formula gives us:

\[ W = \frac{V}{L \times D} \]

### Step 4: Substitute the Known Values
Now we can substitute the known values into the equation:

\[ W = \frac{126 \text{ m}^3}{8 \text{ m} \times 3.5 \text{ m}} \]

### Step 5: Calculate the Denominator
First, calculate the product of length and depth:

\[ 8 \text{ m} \times 3.5 \text{ m} = 28 \text{ m}^2 \]

### Step 6: Calculate the Width
Now substitute this back into the width formula:

\[ W = \frac{126 \text{ m}^3}{28 \text{ m}^2} \]

Calculating this gives:

\[ W = 4.5 \text{ m} \]

### Conclusion
The width of the reservoir is \( 4.5 \text{ m} \).

---