The given area of the farm, A_0=1 hectare.
The fraction of the farm for cultivating tomatoes = 1/2
The fraction of the farm for cultivating lettuce = 2/5
The remaining fraction of farm for onion = 1-(1/2+2/5)=1/10
Therefore, the fraction of farm dedicated to onion is 1/10.
Now, the area dedicated to tomatoes = 1/2 of the area of land.
=1/2 x 1 = 1/2 hectare.
The area dedicated to lettuce = 2/5 of the area of land.
=2/5 x 1 = 2/5 hectare.
The area dedicated to onion = 1/10 of the area of land.
=1/10 x 1 = 1/10 hectare.