Using the percentage concept, it is found that 1 serving of walnuts provides 10% of daily calories.
The percentage of an amount a over a total amount b is given by a multiplied by 100% and divided by b, that is:
[tex]P = \frac{a}{b} \times 100\%[/tex]
In this problem, one serving has 21 grams, each with 10 calories, hence the number of calories is given by:
C = 21 x 10 = 210 calories.
Hence, out of a 2,100 calorie diet, the percentage is given by:
[tex]P = \frac{210}{2100} \times 100\% = 10\%[/tex]
More can be learned about percentages at https://brainly.com/question/10491646
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