In the school hall, chairs were arranged in rows of 15. During a function, 21 chairs were added to accommodate the number of people. The chairs were rearranged to form rows of 13. As a result, there were 3 more rows.
- How many chairs were there in the extra 3 rows?
- How many chairs were there in the school hall in the end?
|
First arrangement |
Second arrangement |
Number |
1 u |
1 u + 3 |
Value |
15 |
13 |
Total value |
15 u |
13 u + 39 |
(a)
Number of chairs in the extra 3 rows
= 3 x 13
= 39
(b)
Total number of chairs in the first arrangement
= 1 u x 15
= 15 u
Total number of chairs in the second arrangement
= 13(1 u + 3)
= 13 u + 39
If 21 chairs were included in the first arrangement, the total number of chairs in the first arrangement and the second arrangement will be the same.
15 u + 21 = 13 u + 39
15 u - 13 u = 39 - 21
2 u = 18
1 u = 18 ÷ 2 = 9
Number of chairs in the school hall in the end
= 9 x 15 + 21
= 135 + 21
= 156
Answer(s): (a) 39; (b) 156