The average number of pages Ivory read in a certain number of days was 20. In the next three days, Ivory read another 30 pages. As a result, the average number of pages she read decreased to 15. How many days did Ivory read in total?
| |
At first |
In the end |
| Number |
1 u |
1 u + 3 |
| Value |
20 |
15 |
| Number x value |
20 u |
15 u + 45 |
Number of days that Ivory read at first = 1 u
Number of pages that Ivory read at first
= 1 u x 20
= 20 u
Number of pages that Ivory read in the end = 20 u + 30
Number of days that Ivory read in the end = 1 u + 3
Number of pages that Ivory read in the end
= 15 x (1 u + 3)
= 15 u + 45
20 u + 30 = 15 u + 45
20 u - 15 u = 45 - 30
5 u = 15
1 u = 15 ÷ 5 = 3
Number of days that Ivory read in the end
= 1 u + 3
= 3 + 3
= 6
Answer(s): 6
