Let the original volume of the raindrop be ′x′ ml. Therefore, initial volume of water in the raindrop will be 0.75x ml. Remaining volume of water after evaporation= (0.75x−2) ml Remaining volume of water is 70% of (x−2) ml. 0.75x−2=(x−2)×0.7 ⇒x=12 .