How does the ratio of h to o atoms in starch compared with the ratio in water?

the same The formula for starch is C6H10O5 which has a ratio of 10 to 5 which reduces to 2 to 1 for the hydrogen to oxygen ratio. The formula for water is H2O which also has the ratio of 2 to 1 for hydrogen. Since the ratios are the same, the answer to the question is "the same". The name used for the category of nutrient that starch falls under should give a strong clue to the chemical formula. It's carbohydrate.