A man bought a watermelon weighing 3 kgs. when he bought the watermelon it contains 40 %of water , after some days due to summer the %of comes down to 20. then find the weight of water melon now?

formula is A =P/Q if A is constant p/q is inversely proportional to each other.
here constant is pulp
PULP =TOTAL *PULP %
80% 60%
- ----- ------
60% 80%
BY further simplification it comes to the fraction of 2/1
:-intially 2 parts =3 kgs , now 1 part=1.5kgs.. so answer is 1.5kgs