There were some rows of benches in a hall. Each row had 9 benches. When Risa brought in 4 extra benches and rearranged all the benches, there were 5 benches in each row and 4 more rows than before. How many benches were there at first?
| |
First
arrangement |
Second
arrangement |
| Number |
1 u |
1 u + 4 |
| Value |
9 |
5 |
| Total value |
9 u |
5 u + 20 |
If another 4 benches are added in the first arrangement, the total number of benches in the first arrangement and the second arrangement will be the same.
9 u + 4 = 5 u + 20
9 u - 5 u = 20 - 4
4 u = 16
1 u = 16 ÷ 4 = 4
Number of benches at first
= 9 u
= 9 x 4
= 36
Answer(s): 36
