PSLEIn a school hall, chairs were arranged in rows such that there were exactly 21 chairs in each row. For a concert, Elijah removed 7 chairs from the school hall and rearranged all the chairs. There are now exactly 14 chairs in each row and 10 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 + 10 |
Value |
21 |
14 |
Total value |
21 u - 7 |
14 u + 140 |
Number of rows at first = 1 u
Number of rows in the end = 1 u + 10
Number of chairs at first after the 7 chairs were removed
= 21 x 1 u - 7
= 21 u - 7
Number of chairs in the end
= 14 x (1 u + 10)
= 14 u + 140
The total number of chairs is equal.
21 u - 7 = 14 u + 140
21 u - 14 u = 140 + 7
7 u = 147
1 u = 147 ÷ 7 = 21
Number of chairs in the end
= 14 u + 140
= 14 x 21 + 140
= 434
Answer(s): 434