The average number of pages Mary read in a certain number of days was 15. In the next eight days, Mary read another 42 pages. As a result, the average number of pages she read decreased to 12. How many days did Mary read in total?
| |
At first |
In the end |
| Number |
1 u |
1 u + 8 |
| Value |
15 |
12 |
| Number x value |
15 u |
12 u + 96 |
Number of days that Mary read at first = 1 u
Number of pages that Mary read at first
= 1 u x 15
= 15 u
Number of pages that Mary read in the end = 15 u + 42
Number of days that Mary read in the end = 1 u + 8
Number of pages that Mary read in the end
= 12 x (1 u + 8)
= 12 u + 96
15 u + 42 = 12 u + 96
15 u - 12 u = 96 - 42
3 u = 54
1 u = 54 ÷ 3 = 18
Number of days that Mary read in the end
= 1 u + 8
= 18 + 8
= 26
Answer(s): 26
