Fun Kids Puzzle: Container Weight Calculation (Q48)

This is one simple puzzle specially for kids.

Lets say x is weight of container which is wanted and w is water

so in first container w+c=160 and in second container w/2+c=90 or w+2c=180gr

if w+c=160 then w=160-c

so lets continue with second container but instead of w we put 160-c

160-c+2c=180

c=20gram

Answer: weight of container(c) is 20gram