PSLEIn a school hall, chairs were arranged in rows such that there were exactly 20 chairs in each row. For a concert, Tom removed 4 chairs from the school hall and rearranged all the chairs. There are now exactly 9 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 |
20 |
9 |
Total value |
20 u - 4 |
9 u + 117 |
Number of rows at first = 1 u
Number of rows in the end = 1 u + 13
Number of chairs at first after the 4 chairs were removed
= 20 x 1 u - 4
= 20 u - 4
Number of chairs in the end
= 9 x (1 u + 13)
= 9 u + 117
The total number of chairs is equal.
20 u - 4 = 9 u + 117
20 u - 9 u = 117 + 4
11 u = 121
1 u = 121 ÷ 11 = 11
Number of chairs in the end
= 9 u + 117
= 9 x 11 + 117
= 216
Answer(s): 216