Step-by-step explanation:
consider the amount of water present in the pond initially as 'x'.
so,
x - (x*25/100) = 1650 litres
x - 25x/100 = 1650 litres
(take LCM and add)
100x/100 - 25x/100 = 1650 litres
75x/100 = 1650 litres
75x = 1650*100 litres
x = 165000/75
= 2200 litres
therefore, there was initially 2200 litres of water in the pond.