Some identical colouring books can be arranged in exactly 15 per row. If the same number of colouring books is arranged in rows of 10 colouring books each, there will be 4 more rows and 5 colouring books left over. How many colouring books are there altogether?
| |
15 per row |
10 per row |
| Number |
1 u |
1 u + 4 |
| Value |
15 |
10 |
| Total value |
15 u |
10 u + 40 + 5 |
Number of rows if the colouring books are arranged in rows of 15 = 1 u
Number of rows if the colouring books are arranged in rows of 10 = 1 u + 4
Total number of colouring books if they are arranged in rows of 15
= 15 x 1 u
= 15 u
Total number of colouring books if they are arranged in rows of 10
= 10 x (1 u + 4) + 5
= 10 u + 40 + 5
= 10 u + 45
The total number of colouring books remains the same for both cases.
15 u = 10 u + 45
15 u - 10 u = 45
5 u = 45
1 u = 45 ÷ 5 = 9
Total number of colouring books
= 15 u
= 15 x 9
= 135
Answer(s): 135
