Question 333594
in your information, such as grams of carbohydrates you show 30.g, so you are not showing the fraction of grams, ditto for fat and protein, so that is probably where your computations did not come out to the book's answer of 280.
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by the way, the relationship of calories to grams of carbo, fat, protein is "calories" not Kcal which implies 1000 calories per gram.
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as far significant figures, you should always carry out yoru computations to at least one more decimal place than the original data, and then you can round "at the end" of the computation.  Otherwise you carry rounding errors which can magnify with each calculation.