PSLEIn a school hall, chairs were arranged in rows such that there were exactly 20 chairs in each row. For a concert, Jeremy removed 7 chairs from the school hall and rearranged all the chairs. There are now exactly 11 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 |
20 |
11 |
Total value |
20 u - 7 |
11 u + 110 |
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
= 20 x 1 u - 7
= 20 u - 7
Number of chairs in the end
= 11 x (1 u + 10)
= 11 u + 110
The total number of chairs is equal.
20 u - 7 = 11 u + 110
20 u - 11 u = 110 + 7
9 u = 117
1 u = 117 ÷ 9 = 13
Number of chairs in the end
= 11 u + 110
= 11 x 13 + 110
= 253
Answer(s): 253