Brian can read 80 pages in 2 hours. How many pages can he read in 3.5 hours?
To find out how many pages Brian can read in 3.5 hours, we first need to determine his constant reading rate. We are given that he can read 80 pages in 2 hours. The rate \(r\) is calculated by dividing the total number of pages \(P\) by the time \(t\):
\[r = \frac{P}{t} = \frac{80 \text{ pages}}{2 \text{ hours}} = 40 \text{ pages per hour}.\]
Now that we have established Brian's reading rate is 40 pages per hour, we can calculate how many pages he reads in 3.5 hours. Using the relationship \(P = r \times t\), where \(r = 40\) pages/hour and \(t = 3.5\) hours:
\[P = 40 \frac{\text{pages}}{\text{hour}} \times 3.5 \text{ hours} = 140 \text{ pages}.\]
Therefore, Brian can read 140 pages in 3.5 hours. Comparing this to the given options, we confirm that 140 pages is the correct answer.
Understanding how to use constant rates is very useful in everyday life. For example, if you know the fuel consumption rate of your car (e.g., 30 miles per gallon), you can easily calculate how many miles you can travel with a certain amount of fuel (e.g., 10 gallons). Similarly, knowing your speed allows you to estimate travel times, helping you plan your day more efficiently. These calculations are fundamental in budgeting resources like time, money, and materials.