A person on a diet loses 15 lb in 3.5 months. Calculate the average weight loss in milligrams per second (mg/s).

The average weight loss is 0.739 mg/s.

The total weight lost by the individual = 15 lb

To convert Ib to mg

1 Ib = 453592 mg

15 lb = 15 lb * 453592 mg/ 1 Ib

= 6803880 mg

The time taken for the weight loss = 3.5 months

Number of seconds in 3.5 months = 9.198 * 10^6 seconds

Hence;

Average weight loss in milligrams per second (mg/s);

Weight lost/ time taken

6803880 mg/9.198 * 10^6 seconds

= 0.739 mg/s

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i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)