What Fraction of a Water Molecule's Mass is Hydrogen?

sxc656
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Hi, see attachment for questions/equations and my attempt.
I have had a go at this question but cannot get the correct answer, could someone be kind enough to point out my mistake and point me in the right direction. Cheers
(sorry for poor pic quality)
 

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What fraction of the mass of each water molecule consists of hydrogen? It's not 1/18.
 
diazona said:
What fraction of the mass of each water molecule consists of hydrogen? It's not 1/18.

2/18. Thank You
 
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