for each experiment there are four possibilities :- {HH, HT,TH,TT}
so probability of getting +2 is 1/4 ,
probability of +1 is 1/2
probability of -3 is 1/4
so average amount in each experiment is (1/4)*2 + (1/2)*1 -(1/4)*3 = 1/4
so average amount for 100 trials = 100*(1/4)= rs 25