Some identical story books can be arranged in exactly 13 per row. If the same number of story books is arranged in rows of 8 story books each, there will be 5 more rows but short of 5 story books. How many story books are there altogether?
|
13 per row |
8 per row |
Number |
1 u |
1 u + 5 |
Value |
13 u |
8 |
Total value |
13 u |
8 u + 40 - 5 |
Number of rows if the story books are arranged in rows of 13 = 1 u
Number of rows if the story books are arranged in rows of 8 = 1 u + 5
Total number of story books if they are arranged in rows of 13
= 13 x 1 u
= 13 u
Total number of story books if they are arranged in rows of 8
= 8 x (1 u + 5) - 5
= 8 u + 40 - 5
= 8 u + 35
The total number of story books remains the same for both cases.
13 u = 8 u + 35
13 u - 8 u = 35
5 u = 35
1 u = 35 ÷ 5 = 7
Total number of story books
= 13 u
= 13 x 7
= 91
Answer(s): 91