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Wednesday, February 10, 2010

Ai Tong Sch 2009 P6 CA1 Math Paper 2 Q16

The number of pupils in Team A to the number of pupils in Team B is in the ratio of 7:6. If 45 pupils are transferred from Team A to Team B, the ratio will become 2:3. How many pupils are there altogether?


Note - "Before" is multiplied by 5, while "After" is multiplied by 13 so as to have an equal number of total units of 65 each. The total number of units for "Before" and "After" are the same because there was no increase or decrease in the total number of pupils before or after the transfer.

Team A had a decrease of

35 units – 26 units --> 45 (pupils)
9 units --> 45
1 unit --> 45 divided by 9 = 5

Total number of pupils
Team A + Team B
26 units + 39 units --> 65 units
65 units --> 5 x 65 = 325

Answer: 325 pupils

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