One chicken lays two eggs in three days. 
How many eggs do three chickens lay in nine days?

18 eggs.

1 chicken lays 2 eggs in 3 days, so 3 chickens lay 3×2=6 eggs in 3 days. In 9 days, these 3 chickens lay 3 times as much eggs as in 3 days. Conclusion: three chickens lay 3×6=18 eggs in nine days.


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