PSLEIn a school hall, chairs were arranged in rows such that there were exactly 21 chairs in each row. For a concert, Carl brought 9 more chairs into the school hall and rearranged all the chairs. There are now exactly 10 chairs in each row and 13 more rows than before. How many chairs are there in the school hall for the concert in the end?
|
Before |
After |
Number |
1 u |
1 u + 13 |
Value |
21 |
10 |
Total value |
21 u + 9 |
10 u + 130 |
Number of rows at first = 1 u
Number of rows in the end = 1 u + 13
Number of chairs at first after the 9 chairs were brought in
= 21 x 1 u + 9
= 21 u + 9
Number of chairs in the end
= 10 x (1 u + 13)
= 10 u + 130
The total number of chairs is equal.
21 u + 9 = 10 u + 130
21 u - 10 u = 130 - 9
11 u = 121
1 u = 121 ÷ 11 = 11
Number of chairs in the end
= 10 u + 130
= 10 x 11 + 130
= 240
Answer(s): 240