Question

In order to complete a reading assignment on time, Terry planned to read 90 pages per day. However, she read only 75 pages per day at first, leaving 690 pages to be read during the last 6 days before the assignment was to be completed. How many days in all did Terry have to complete the assignment on time?

Answer 1

Say Terry read at the rate of 75 pages per day for d days. 

Now, in d days she read 75d pages, and since after that 690 pages were left, then the number of pages in the book is 75d+690.

Next, we also know that she had d+6 days for the assignment. Since Terry planned to read 90 pages per day for this number of days, then the number of pages in book is also equal to 90(d+6).

So, we have that 75d+690 = 90(d+6). Solving the linear equation, we get d = 10.

Thus, the total number of days that she has to complete the assignment on time is d+6 or 10 + 6 = 16 days.