Daily Dose of Solved Questions Nov 16

A vessel full of water weighs $40\:kg$ . If it is one-third filled, its weight becomes $20\:kg$ . What is the weight of the empty vessel?

$(a)$ $10\:kg$
$(b)$ $15\:kg$
$(c)$ $20\:kg$
$(d)$ $25\:kg$

CSAT Mantra