The width of a door is 0.91 m. The door is opened through an angle of 72°. What is the length welds the tip of the door sweeps through?

$$L = 0.91 \text{ m} \times \frac{2\pi}{5}$$

Using $\pi \approx 3.14159$:

$$L = 0.91 \times \frac{2 \times 3.14159}{5}$$ $$L = 0.91 \times \frac{6.28318}{5}$$ $$L = 0.91 \times 1.256636$$ $$L \approx 1.1435 \text{ m}$$

Rounding to two decimal places, $L \approx 1.14 \text{ m}$.
The final answer is $\boxed{\text{B. 1.14 m}}$.

Diameter $D = 40 \text{ cm}$, so radius $r = \frac{40}{2} = 20 \text{ cm}$.

$$A_{base} = \pi r^2 = \pi (20 \text{ cm})^2 = 400\pi \text{ cm}^2$$

Height of water $h = 42 \text{ cm}$.

$$A_{lateral} = 2\pi r h = 2\pi (20 \text{ cm})(42 \text{ cm}) = 1680\pi \text{ cm}^2$$

$$A_{total} = A_{base} + A_{lateral} = 400\pi \text{ cm}^2 + 1680\pi \text{ cm}^2 = 2080\pi \text{ cm}^2$$

Using a calculator value for $\pi \approx 3.14159265$:

$$A_{total} = 2080 \times 3.14159265 \approx 6534.5127 \text{ cm}^2$$

Rounding to two decimal places, $A_{total} \approx 6534.51 \text{ cm}^2$.
The final answer is $\boxed{\text{C. 6534.51}}$.

Length $l = 8.5 \text{ cm}$, width $w = 5 \text{ cm}$, height $h = 13 \text{ cm}$.

$$V = l \times w \times h = 8.5 \text{ cm} \times 5 \text{ cm} \times 13 \text{ cm}$$ $$V = 42.5 \text{ cm}^2 \times 13 \text{ cm}$$ $$V = 552.5 \text{ cm}^3$$

Since $1 \text{ litre} = 1000 \text{ cm}^3$:

$$V_{litres} = \frac{552.5 \text{ cm}^3}{1000 \text{ cm}^3/\text{litre}} = 0.5525 \text{ litres}$$

Comparing this value to the given options, 0.51 litres is the closest option.
The final answer is $\boxed{\text{A. 0.51 litres}}$.

2 zimekamilika. Zimebaki 3 leo — tuma inayofuata.