In the school hall, chairs were arranged in rows of 12. During a function, 39 chairs were added to accommodate the number of people. The chairs were rearranged to form rows of 9. As a result, there were 9 more rows.
- How many chairs were there in the extra 9 rows?
- How many chairs were there in the school hall in the end?
|
First arrangement |
Second arrangement |
Number |
1 u |
1 u + 9 |
Value |
12 |
9 |
Total value |
12 u |
9 u + 81 |
(a)
Number of chairs in the extra 9 rows
= 9 x 9
= 81
(b)
Total number of chairs in the first arrangement
= 1 u x 12
= 12 u
Total number of chairs in the second arrangement
= 9(1 u + 9)
= 9 u + 81
If 39 chairs were included in the first arrangement, the total number of chairs in the first arrangement and the second arrangement will be the same.
12 u + 39 = 9 u + 81
12 u - 9 u = 81 - 39
3 u = 42
1 u = 42 ÷ 3 = 14
Number of chairs in the school hall in the end
= 14 x 12 + 39
= 168 + 39
= 207
Answer(s): (a) 81; (b) 207