Question

A cistern contains 50 litres of water. 5 litres of water is taken out of it and replaced by wine. the process is repeated again. find the proportion of wine and water in the resulting mixture

Answer 1

total watar 50 litres
then we take out 5 litre water
and mix 5 litre wine
so we have 50 litres mixture of water &wine
we repeat this process
then watar 45- 4=41
wine is5-1=4
and 4+5=9

so
mixture=watàr+wine
50=41+9

so

watàr/wine=41/9

Answer 2

5 ltr of 50ltr 10%  

therefore wine is 10% CONC. ( 5LTR wine)

the conc remains same even if you remove excess mixture.

youll hv 45ltr mixture i.e 4.5 ltr wine(10%) . add 5 ltr wine.

so total 9.5 ltr wine and 40.5 ltr water.

9.5::40.5

19::81

this is the ans.