A storage tank weighs 40 kg when it is one-third full of oil. When completely filled with the same oil, it weighs 100 kg. What is the weight of the empty tank?
(a) 15 kg
(b) 10 kg
(c) 20 kg
(d) 25 kg
Correct Answer : Option b
Let the weight of the empty tank be x kg and the weight of the full oil content be y kg.
Since one-third of the tank filled weighs 40 kg,
we have: x + 1/3y = 40 Also, when the tank is completely filled, its weight is 100 kg: x + y = 100
On solving we get,
y = 90
Now substitute y = 90
into x + y = 100x + y = 100:
x = 10 kg.
Hence, option b is correct.
