PSLEThere were a total of 128 tables and chairs in a canteen. There were 3 times as many chairs as tables. After 21 chairs and some tables were thrown away, there were 5 times as many chairs as tables left. How many tables were thrown away from the canteen?
|
Tables |
Chairs |
Total |
Before |
1 u |
3 u |
128 |
Change |
- ? |
- 21 |
|
After |
1 p |
5 p |
|
Number of tables and chairs at first
= 3 u + 1 u
= 128
4 u = 128
1 u = 128 ÷ 4 = 32
Number of chairs at first
= 3 u
= 3 x 32
= 96
Number of chairs left
= 96 - 21
= 75
5 p = 75
1 p = 75 ÷ 5 = 15
Number of tables thrown away from the canteen
= 32 - 15
= 17
Answer(s): 17