In a monogamous culture, 90% of the adults are married. The average number of children per family is five and over-population is a threat. Programs to encourage birth-control have been ineffective. It has been suggested that this failure is due to these programs ignoring a tradition that values male children very highly, so that every parent wants to have at least one son. It is proposed that couples be encouraged to use birth-control measures after the birth of their first son. If this proposal is widely accepted in the culture, we may expect that:

A) the rate of population increase will be slowed, and future generations will contain a disproportionately high number of females.

B) the rate of population increase will be slowed, and the gender balance in future generations will remain as it is at present.

C) the rate of population growth will remain the same, and future generations will contain a disproportionately high number of females.

D) there will be no significant effect either on population growth or on gender balance.

E) the population will decline precipitously, because approximately half of all families will have only a single child.

Aswers with explanations please.

E.

1. Popluation growth: Using birth control with any rule is going to reduce the population growth, compared to not using birth control at all. That too, where the average child/family is 5, if a child is born as male anywhere between 1 to 5, further growth is stopped in that family.
So, C and D goes off.

2. Male/Female growth: The the probablity of getting a male child is 1/2. 50% People are going to keep reaping(?) female child until they successfully get a male child. Whereas the other 50% family is not going to have any female child at all - just the first male child.
These two balance each other and hence there is not going to be any difference in the male/female ratio.
So, A and B goes off.

E is a good inference.

[Eg: Consider 800 families,
Child1: 400 gets M and birth control is used. Another 400 gets F and continues to explore.
Child2: The 400F1 now gets split, 200M (birth control exercised) and 200F2 (continue exploration)
Child3: 200=100M+100F
Child4: 100=50M+50F
Child5: 50=25M+25F
Inference:
a. If you see atlast, there is an equal balance of 775M and 775F childs -- supports elimnating A and B.
b. Also see that 775 families used birth control once they got a M child somewhere, due to the policy; they would have otherwise continued further exploration -- explains the precipitous decline in population growth (E).]

try for some more time. this is slightly tricky.

see explanations here:

http://www.gmatclub.com/phpbb/viewtopic ... b486070180