To determine how much the water level is lowered when 1 litre of water is drawn off, given the cylindrical bottle's diameter is 28 cm, we proceed as follows:

Given:

• Diameter = 28 cm → Radius $r = \frac{28}{2} = 14 \, \text{cm}$

• Volume of water removed = 1 litre = 1000 cm³

• Formula for the volume of a cylinder:
  $V = \pi r^2 h$ where $V$ is the volume, $r$ is the radius, and $h$ is the height (water level drop in this case).

• $\pi = \frac{22}{7}$

Step 1: Rearrange the formula for $h$ (height)

We know the volume removed and the radius. Substituting into the formula:
$V = \pi r^2 h$ Rearranging for $h$:
$h = \frac{V}{\pi r^2}$

Step 2: Substitute known values

• $V = 1000 \, \text{cm}^3$
• $r = 14 \, \text{cm}$
• $\pi = \frac{22}{7}$

Substitute these into the formula for $h$:
$h = \frac{1000}{\frac{22}{7} \times 14^2}$

Step 3: Simplify step-by-step

1. Calculate $r^2$:
   $14^2 = 196$
2. Multiply $\pi$ and $r^2$:
   $\frac{22}{7} \times 196 = \frac{22 \times 196}{7} = \frac{4312}{7} = 616$
3. Divide the volume $V$ by this result:
   $h = \frac{1000}{616} \approx 1.623 \, \text{cm}$

Final Answer:

The water level is lowered by approximately 1.62 cm.

Let me know if you need further clarification!

Here are 5 related questions for practice:

1. How much water in litres can the cylindrical bottle hold when filled to the top?
2. If 500 cm³ of water is removed, how much will the water level drop?
3. Calculate the surface area of the cylindrical water bottle.
4. What is the volume of the bottle in cubic meters if it is completely filled?
5. If the bottle’s height is doubled, how does the volume change?

Tip: Always keep unit conversions in mind when working with litres and cubic centimeters!