Chapter 1, Problem 28P

To determine

To estimate: The number of liters of water a human drinks in a lifetime.

Answer to Problem 28P

An average human drinks almost a hundred thousand liters of water in his lifetime.

Explanation of Solution

Introduction:

In order to estimate the amount of water an average human being drinks in his lifetime, the following assumptions are made:

First assumption is that for healthy living, one is advised to drink at least 3 liters of water each day.

Therefore, the number of liters of water a human drinks = 3 L.

Second assumption. With the vast improvements seen in health care the average lifetime of a human has increased over the period of time.

Hence, assume the average lifetime of a human to be 70 years.

If a human being, who consumes 3 L of water each day over a period of 70 years, the total amount he consumes in his lifetime is given by,

  $\begin{array}{c}\text{Amount of water}=\left(\frac{3\text{ L}}{1\text{ day}}\right)\left(\frac{365\text{ days}}{1\text{ year}}\right)\left(70\text{ years}\right)\\ =7.7\times {10}^4\text{L}\\ \approx \text{1}\times {\text{10}}^5\text{L}\\ \text{=100,000 L}\end{array}$

Rounding the value to the closest power of 10, one can estimate the amount of water consumed by an average human to be around a hundred thousand litres.

Conclusion:

Thus, an average human drinks almost a hundred thousand of water in his lifetime.