Calculate the energy provided by a slice of bread containing 2 g of protein, 1 g of fat, and 20 g of carbohydrate. record your answer using whole number. kcal

 the energy gained by proteins and carbohydrates differs from the energy gained by fats.
proteins and carbohydrates both give 4 kcal per gram 
fats give 9 kcal per gram
mass of proteins - 2 g
energy given by proteins - 2 g x 4 kcal/g = 8 cal
mass of carbohydrates - 20 g 
energy given by carbohydrates - 20 g x 4 kcal/g = 80 cal
mass of fat - 1 g 
energy given by fat - 1 g x 9 kcal/g = 9 cal
total energy = 8 + 80 + 9 = 97 kcal
energy = 97 kcal