The petrol tank of car having a capacity of $30$ L, has $16$ L petrol. If $8$ L $623$ ml petrol is consumed, how much petrol will be required to fill the tank completely?

Step 1: Finding the amount of petrol left in tank.

Given: Amount of petrol in tank $=16$ L

$=16000$ ml [ $1$L $=1000$ ml ]

The amount of petrol consumed from tank $=8$ L $623$ ml.

$$\begin{gathered} =8000+623 \\ =8623\mathrm{ml} \end{gathered}$$ [ $1$L $=1000$ ml ]

Now, the amount of petrol left in the tank $=$ Amount of petrol in tank $-$The amount of petrol consumed from tank

$$\begin{gathered} =16000-8623 \\ =7377\mathrm{ml} \end{gathered}$$

Step 2: Finding the amount of petrol required to fill the tank completely.

The capacity of petrol tank of car $=30$ L

$=30000$ ml [ $1$L $=1000$ ml ]

So, petrol required to fill the tank completely $=$The capacity of the petrol tank of car $-$ The amount of petrol left in the tank

$$\begin{gathered} =30000-7377 \\ =22623\mathrm{ml} \end{gathered}$$

i.e., $22.623\mathrm{L}$ or $22\mathrm{L}623\mathrm{ml}$

Hence, $22.623\mathrm{L}$ petrol will be required to fill the tank completely.