The average number of pages Sarah read in a certain number of days was 12. In the next three days, Sarah read another 72 pages. As a result, the average number of pages she read increased to 14. How many days did Sarah read in total?
| |
At first |
In the end |
| Number |
1 u |
1 u + 3 |
| Value |
12 |
14 |
| Number x value |
12 u |
14 u + 42 |
Number of days that Sarah read at first = 1 u
Number of pages that Sarah read at first
= 1 u x 12
= 12 u
Number of pages that Sarah read in the end = 12 u + 72
Number of days that Sarah read in the end = 1 u + 3
Number of pages that Sarah read in the end
= 14 x (1 u + 3)
= 14 u + 42
14 u + 42 = 12 u + 72
14 u - 12 u = 72 - 42
2 u = 30
1 u = 30 ÷ 2 = 15
Number of days that Sarah read in the end
= 1 u + 3
= 15 + 3
= 18
Answer(s): 18
