Question
PSLE
The average mass of 3 boys, David, Adam, Christian, is 50 kg. David is lighter than Adam by 9 kg. The total mass of David and Adam is the same as the mass of Christian. What is the mass of David?
2 m

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PSLE
The average mass of 3 boys, David, Adam, Christian, is 50 kg. David is lighter than Adam by 9 kg. The total mass of David and Adam is the same as the mass of Christian. What is the mass of David?