Chapter 7.4, Problem 54PPE

To determine

To think: During one year, about 163 million adults over 18 years old in the United States spent

a total of about 93 billion hours online at home. On average, how many hours per day

did each adult spend online at home?

Answer to Problem 54PPE

The required answer is: an adult spends 1.56 hours per day online

Explanation of Solution

Given information:

The given information: 163 million adults over 18 years spent 93 billion hours online at home

Calculation:

163 million adults $=163000000$

  $=1.63\times {10}^8$

(Scientific notation)

93 billion hours $=93000000000$

  $=9.3\times {10}^{10}$

(Scientific notation)

  $\frac{9.3\times {10}^{10}}{1.63\times {10}^8}=\frac{9.3}{1.63}\times {10}^{10-8}$

(Subtract exponents when dividing powers with the same base)

  $\begin{array}{l}=\frac{9.3}{1.63}\times {10}^2\\ =5.7055\times {10}^2\\ =5.7055\times 100\\ =570.55\end{array}$

(Simplify)

An adult spends 570.55 hours online in a year

Average hours spent in a day $=\frac{570.55}{365}$

(Divide by days in a year which is 365 days)

  $=1.56$

(Simplify)

Therefore on average, an adult spends 1.56 hours per day online at home.