Question

a drum of kerosene is 3 over 4 full than 30 litre of oil is drawn from
it is 7 over 2 full find the capacity of the drum

Answer 1

Let Capacity of Drum = X litres.

Initially, Drum was $\frac{3X}{4}$ part filled.

30 litres oil drawn then it become, $\frac{7X}{12}$ part.

Now, according to question,

⇒ $\frac{3X}{4} - \frac{7X}{12} = 30$

⇒ $\frac{9X - 7X}{12} = 30$

⇒ $2X = 360$

∴ $X = 180$ litres

An alternate method:

Here, $\frac{3}{4} + \frac{1}{4} =$ Full Capacity of Drum 

So, $\frac{3}{4} =$ Full Capacity of Drum $- \frac{1}{4}$
⇒ $\frac{3}{4} - 30 = \frac{7}{12}$ 

Thus, (Full Capacity of Drum $- \frac{1}{4}$) $- 30 = \frac{7}{12}$

Now, Let full capacity of drum is x.
 
So, $(x - \frac{1}{4}x) - \frac{7}{12} x = 30$ litres 
⇒ $x (1 - \frac{1}{4} - \frac{7}{12}) = 30$ 
⇒ $\frac{x (12 - 3 - 7)}{12} = 30$
⇒ $\frac{1}{6} x = 30$ 

∴ x = 180 litres

Hope This Helps :)