Question

Calculate the number of calories present in a chocolate chip cookie that contains 16 g carbohydrate, 3 g protein, and 7 g fat. Express your answer to one significant figure and include the appropriate units.

Answer 1

As per USDA site, these are the calories aporte by type of nutrient:

Fat: 9 cal / g
Protein: 4 cal / g
Carbohydrates: 4 cal / g

Then,

16 g Carb.  * 4 cal / g =    64 cal
3 g protein  * 4 cal / g =    12 cal
7 g fat         * 9 cal / g =    63 cal
----------------                    -----------
26 g                                 139 cal

Rounded to one significant figure 100 cal.

Answer: 100 cal.