I was doing a question on Markov's Inequality where I have to give the answer and the question is stated as follows :
A town of 30 families, the average household size is 2.5. What is the largest number of families that can have at least 4 members according to Markov’s Inequality?
According to this formula P(X >= a) = µ/a
here µ=2.5 and and a=4 thus P(X >= a) = 0.625
that is 30*0.625=18.75 and since 18.75 is not a integer as number of family can't be in fraction therefore answer should be 18 but the question is showing incorrect answer.
I don't understand what am I doing wrong.
Thanks in advance.