What is the basic unit of length in the metric system? What is the length of this line in: (i) Centimetres? (ii) Millimetres? (iii) Metres? Name the instruments that are used to measure the following. (i) Length of a soccer field (ii) Things that are not straight

    $$
    1 \text{ cm} = 10 \text{ mm}
    $$
    $$
    3 \text{ mm} = \frac{3}{10} \text{ cm} = 0.3 \text{ cm}
    $$

    $$
    3 \text{ cm} + 0.3 \text{ cm} = 3.3 \text{ cm}
    $$
    The length is $\boxed{\text{3.3 cm}}$.

*   **(ii) Millimetres?**

    $$
    1 \text{ cm} = 10 \text{ mm}
    $$
    $$
    3.3 \text{ cm} = 3.3 \times 10 \text{ mm} = 33 \text{ mm}
    $$
    The length is $\boxed{\text{33 mm}}$.

*   **(iii) Metres?**

    $$
    1 \text{ m} = 100 \text{ cm}
    $$
    $$
    3.3 \text{ cm} = \frac{3.3}{100} \text{ m} = 0.033 \text{ m}
    $$
    The length is $\boxed{\text{0.033 m}}$.