Convert these units of measurement.

To convert from $\text{mm}$ to $\text{cm}$, divide by 10. $780 \text{ mm} = \frac{780}{10} \text{ cm}$

$$
780 \text{ mm} = \boxed{78 \text{ cm}}
$$

2. Convert $45 \text{ cm}$ to $\text{ mm}$

To convert from $\text{cm}$ to $\text{mm}$, multiply by 10. $45 \text{ cm} = 45 \times 10 \text{ mm}$

$$
45 \text{ cm} = \boxed{450 \text{ mm}}
$$

3. Convert $25000 \text{ cm}$ to $\text{ m}$

To convert from $\text{cm}$ to $\text{m}$, divide by 100. $25000 \text{ cm} = \frac{25000}{100} \text{ m}$

$$
25000 \text{ cm} = \boxed{250 \text{ m}}
$$

4. Convert $8 \text{ m}$ to $\text{ cm}$

To convert from $\text{m}$ to $\text{cm}$, multiply by 100. $8 \text{ m} = 8 \times 100 \text{ cm}$

$$
8 \text{ m} = \boxed{800 \text{ cm}}
$$

5. Convert $7 \text{ km}$ to $\text{ m}$

To convert from $\text{km}$ to $\text{m}$, multiply by 1000. $7 \text{ km} = 7 \times 1000 \text{ m}$

$$
7 \text{ km} = \boxed{7000 \text{ m}}
$$

6. Convert $135000 \text{ m}$ to $\text{ km}$

To convert from $\text{m}$ to $\text{km}$, divide by 1000. $135000 \text{ m} = \frac{135000}{1000} \text{ km}$

$$
135000 \text{ m} = \boxed{135 \text{ km}}
$$

7. Convert $0.5 \text{ cm}$ to $\text{ mm}$

To convert from $\text{cm}$ to $\text{mm}$, multiply by 10. $0.5 \text{ cm} = 0.5 \times 10 \text{ mm}$

$$
0.5 \text{ cm} = \boxed{5 \text{ mm}}
$$

8. Convert $0.5 \text{ km}$ to $\text{ m}$

To convert from $\text{km}$ to $\text{m}$, multiply by 1000. $0.5 \text{ km} = 0.5 \times 1000 \text{ m}$

$$
0.5 \text{ km} = \boxed{500 \text{ m}}
$$

9. Convert $6.5 \text{ cm}$ to $\text{ mm}$

To convert from $\text{cm}$ to $\text{mm}$, multiply by 10. $6.5 \text{ cm} = 6.5 \times 10 \text{ mm}$

$$
6.5 \text{ cm} = \boxed{65 \text{ mm}}
$$

10. Convert $2.5 \text{ km}$ to $\text{ m}$

To convert from $\text{km}$ to $\text{m}$, multiply by 1000. $2.5 \text{ km} = 2.5 \times 1000 \text{ m}$