Question

0.8 portion of a tank is filled with water.if 25 litres of water is taken out from the tank ,14 litres of excess water over the half filled up tank remains in it.find the capacity of the tank

Answer 1

The tanks was filled to 0.8th portion.

when 25 liters are removed, 14 liters excess of half the tank is left.
let the capacity of the tank be x.(half of it will be 0.5x)
Therefore if you add half the capacity of the tank plus 14 liters plus 25 liters should give you the original volume:

0.5x + 14 liters + 25 liters = 0.8x
14 + 25 = 0.8x - 0.5x
0.3x = 39 liters
    x = 39/0.3 liters
    x = 130 liters 
Therefore the tank's capacity is 130 liters.

Answer 2

Let the tank capacity  be C liters.
Volume of Water in the tank = 0.8 C  liters

25 liters taken out... so remaining = 0.8 C - 25 liters.
14 liters of excess water over half filled up tank =  14 + C/2   liters.

so  0.8 C - 25 = 14 + C/2
so   0.3 C = 39 liters

        C = 130 liters