With litre of milk, you will need litres of tea. So, together with the milk, you'll get litres of "proper tea".
A typical cup will hold about 200 to 250 ml. So you'll get 4 to 5 cups from a litre. Altogether, then, you'll get around 22 to 28 cups of "proper tea" from a litre of milk.
in proper tea ratio of milk(say m) and tea (say t) is 2:9 or
if milk is 1 litre there for quantity of tea should be
or t= 4.5 litre
so total liquid quantity is 1+4.5 litre =5.5 litre
now suppose there are n cups with volume v (i litre) then 5.5 litre milk can be put in 5.5/v cups
but same formula can be used in different way i.e
so for n=1 i.e if only one cup is used its volume should be 5.5 litre.
if n=2 its volume should be 2.75 litre
in general 5.5 litre of liquid can be filled in any number of cups
therefor answer is
any natural number (according to it 5 is also correct)
(though one may neglect those values of n for which v is non-terminating decimal value.)