Ravi bought 5 kg 300 g apples and 3 kg 250 g mangoes. Suman bought 4 kg 800 g oranges and 4 kg 150 g grapes. Who bought more fruits and by how much.

$$18 \text{ L} = 0.018 \text{ kL}$$

The answer is $\boxed{0.018 \text{ kL}}$.

b) 3 kL 236 L as kilolitres

$$3 \text{ kL} + 0.236 \text{ kL} = 3.236 \text{ kL}$$

The answer is $\boxed{3.236 \text{ kL}}$.

8. Using decimal numbers express:

a) 680 m in kilometres

$$680 \text{ m} = 0.680 \text{ km}$$

The answer is $\boxed{0.680 \text{ km}}$.

b) 110 km 7 m in kilometres

$$110 \text{ km} + 0.007 \text{ km} = 110.007 \text{ km}$$

The answer is $\boxed{110.007 \text{ km}}$.

9. Add:

a) 6.75, 4.3, 2.913

$$\begin{align*} 6.750 \\ 4.300 \\ + 2.913 \\ \hline 13.963 \end{align*}$$

The answer is $\boxed{13.963}$.

b) 0.0804, 0.00026, 0.10073, 0.02065

$$\begin{align*} 0.08040 \\ 0.00026 \\ 0.10073 \\ + 0.02065 \\ \hline 0.20204 \end{align*}$$

The answer is $\boxed{0.20204}$.

10. Subtract:

a) 6.896 from 17.581

$$\begin{align*} 17.581 \\ - 6.896 \\ \hline 10.685 \end{align*}$$

The answer is $\boxed{10.685}$.

b) 0.0093 from 0.045

$$\begin{align*} 0.0450 \\ - 0.0093 \\ \hline 0.0357 \end{align*}$$

The answer is $\boxed{0.0357}$.

11. Simplify:

a) $4.105 + 2.37 - 5.2$

$$6.475 - 5.2 = 1.275$$

The answer is $\boxed{1.275}$.

b) $100 - 3.067 - 33.08 - 21.2$

$$63.853 - 21.2 = 42.653$$

The answer is $\boxed{42.653}$.

12. Ravi bought 5 kg 300 g apples and 3 kg 250 g mangoes. Suman bought 4 kg 800 g oranges and 4 kg 150 g grapes. Who bought more fruits and by how much.

$$5 \text{ kg } 300 \text{ g} = 5.300 \text{ kg}$$ $$3 \text{ kg } 250 \text{ g} = 3.250 \text{ kg}$$ $$\text{Ravi's total} = 5.300 \text{ kg} + 3.250 \text{ kg} = 8.550 \text{ kg}$$

$$4 \text{ kg } 800 \text{ g} = 4.800 \text{ kg}$$ $$4 \text{ kg } 150 \text{ g} = 4.150 \text{ kg}$$ $$\text{Suman's total} = 4.800 \text{ kg} + 4.150 \text{ kg} = 8.950 \text{ kg}$$

$$8.950 \text{ kg} > 8.550 \text{ kg}$$ $$\text{Difference} = 8.950 \text{ kg} - 8.550 \text{ kg} = 0.400 \text{ kg}$$

Suman bought more fruits by $0.400 \text{ kg}$ or $400 \text{ g}$.
The answer is $\boxed{\text{Suman bought more fruits by } 0.400 \text{ kg}}$.

13. A water storage drum which is 35.54 cm long contains water to a depth of 23.5 cm. How far is the water level below the top of the drum?

$$\text{Distance below top} = \text{Total length} - \text{Water depth}$$ $$\text{Distance below top} = 35.54 \text{ cm} - 23.5 \text{ cm}$$

$$\begin{align*} 35.54 \\ - 23.50 \\ \hline 12.04 \end{align*}$$

The water level is $12.04 \text{ cm}$ below the top of the drum.
The answer is $\boxed{12.04 \text{ cm}}$.