Monique is reading a book. The table shows how the number of pages remaining in the book is changing over time.

READING A BOOK

Time (hours) Number of Pages Remaining
0 360
1 320
2 280
3 240
4 200
Which equation describes the relationship between t, the time in hours, and N, the number of pages remaining in the book?

A. N =-40t - 360

B. N = -40t + 360

C. N = 40t + 360

D. N = 40t - 360

1 answer

To determine the equation that describes the relationship between \( t \) (time in hours) and \( N \) (number of pages remaining), we can analyze the data given in the table:

  • At time \( t = 0 \) hours, \( N = 360 \) pages
  • At time \( t = 1 \) hour, \( N = 320 \) pages
  • At time \( t = 2 \) hours, \( N = 280 \) pages
  • At time \( t = 3 \) hours, \( N = 240 \) pages
  • At time \( t = 4 \) hours, \( N = 200 \) pages

From this, we can observe the following:

  • The number of pages decreases by 40 for each hour that passes. For example:
    • From 360 to 320 is a decrease of 40 pages (from \( t = 0 \) to \( t = 1 \))
    • From 320 to 280 is a decrease of 40 pages (from \( t = 1 \) to \( t = 2 \))
    • This pattern continues for all subsequent hours.

Now, we can identify the slope of the line, which represents the rate of change of pages:

  • The slope (rate of change) is \(-40\), indicating that the number of pages remaining decreases by 40 for each hour.

Now, we can use the slope-intercept form of a linear equation:

\[ N = mt + b \]

where \( m \) is the slope and \( b \) is the y-intercept (the number of pages at \( t = 0 \)).

From our data:

  • The slope \( m = -40 \)
  • The y-intercept \( b = 360 \)

Putting these values into the equation:

\[ N = -40t + 360 \]

Thus, the correct equation that describes the relationship between \( t \) and \( N \) is:

B. \( N = -40t + 360 \)