What is the muscle mass of a thirty-year-old man weighing 78 kg if the muscular system is known to be 40% of his body weight?

1. To find the muscle mass of a man weighing 78 kg, you need to find how many kilograms make up 40% of his mass. To do this, divide the weight of a person by 100, get a weight of 1%, and then multiply the resulting value by 40:
78/100 = 0.78 kg / 1%.
2.0.78 * 40 = 31.2 kg.
Answer: The muscle mass of a 78 kg man is 31.2 kg.