Question

Which of the following is the best estimate for the mass of all the people living on the Earth?

• A. $2\ast {10}^{8}kg$
• B. $1\ast {10}^{9}kg$
• C. $2\ast {10}^{10}kg$
• D. $3\ast {10}^{11}kg$
• E. $4\ast {10}^{12}kg$

Answer 1

Answer: (D)

$3\ast {10}^{11}kg$

The population is about $6$ billion = $6\ast {10}^9$. Assuming about $100$ lb per person = about $50$ kg per person ($1$ kg has the weight of about $2.2$ lb), the total mass is about $(6\ast {10}^9)\left(50kg\right)=3\ast {10}^{11}kg$,

answer (d).