The average number of pages Jade read in a certain number of days was 13. In the next three days, Jade read another 81 pages. As a result, the average number of pages she read increased to 15. How many days did Jade read in total?
| |
At first |
In the end |
| Number |
1 u |
1 u + 3 |
| Value |
13 |
15 |
| Number x value |
13 u |
15 u + 45 |
Number of days that Jade read at first = 1 u
Number of pages that Jade read at first
= 1 u x 13
= 13 u
Number of pages that Jade read in the end = 13 u + 81
Number of days that Jade read in the end = 1 u + 3
Number of pages that Jade read in the end
= 15 x (1 u + 3)
= 15 u + 45
15 u + 45 = 13 u + 81
15 u - 13 u = 81 - 45
2 u = 36
1 u = 36 ÷ 2 = 18
Number of days that Jade read in the end
= 1 u + 3
= 18 + 3
= 21
Answer(s): 21
