A chemist mixes two liquids 1 and 2. One litre of liquid 1 weighs 1 kg and one litre of liquid 2 weighs 800 gm. If half litre of the mixture weighs 480 gm, then the percentage of liquid 1 in the mixture, in terms of volume, is

The correct option is 4 (i.e. 80).

Let the volume of liquid 1 in one litre of the mixture be $x$ litres. Since the total volume of the mixture is 1 litre, the volume of liquid 2 will be $1-x$ litres.

We are given:
- 1 litre of liquid 1 weighs 1 kg = 1000 gm. So, the weight of $x$ litres of liquid 1 is $1000x$ gm.
- 1 litre of liquid 2 weighs 800 gm. So, the weight of $1-x$ litres of liquid 2 is $800(1-x)$ gm.

We are also given that half a litre of the mixture weighs 480 gm. Therefore, 1 litre of the mixture weighs:
$2\times 480=960\text{gm}$

Now we can set up the equation for the total weight of 1 litre of the mixture:
$1000x+800(1-x)=960$

Simplifying the equation:
$1000x+800-800x=960$
$200x=160$
$x=\frac{160}{200}=0.8$

Since $x=0.8$ litres, the percentage of liquid 1 by volume in the mixture is:
$0.8\times 100=80\%$