PSLE
In a school hall, chairs were arranged in rows such that there were exactly 25 chairs in each row. For a concert, Zane removed 6 chairs from the school hall and rearranged all the chairs. There are now exactly 8 chairs in each row and 12 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 + 12
Value	25	8
Total value	25 u - 6	8 u + 96

Number of rows at first = 1 u
Number of rows in the end = 1 u + 12

Number of chairs at first after the 6 chairs were removed
= 25 x 1 u - 6
= 25 u - 6

Number of chairs in the end
= 8 x (1 u + 12)
= 8 u + 96

The total number of chairs is equal.

25 u - 6 = 8 u + 96
25 u - 8 u = 96 + 6 
17 u = 102

1 u = 102 ÷ 17 = 6 

Number of chairs in the end
= 8 u + 96
= 8 x 6 + 96
= 144

Answer(s): 144