PSLEIn a school hall, chairs were arranged in rows such that there were exactly 20 chairs in each row. For a concert, Ben removed 4 chairs from the school hall and rearranged all the chairs. There are now exactly 8 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 |
8 |
Total value |
20 u - 4 |
8 u + 80 |
Number of rows at first = 1 u
Number of rows in the end = 1 u + 10
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
= 8 x (1 u + 10)
= 8 u + 80
The total number of chairs is equal.
20 u - 4 = 8 u + 80
20 u - 8 u = 80 + 4
12 u = 84
1 u = 84 ÷ 12 = 7
Number of chairs in the end
= 8 u + 80
= 8 x 7 + 80
= 136
Answer(s): 136