why does rasheed want a boy ? how would life had been different if mariam had a boy ? why does rasheed become abusive ?

Mariam discovers that she is pregnant, and Rasheed is very obvious about his preference for a boy. Rasheed is genuinely happy about the pregnancy and already loves the unborn baby intensely. Most men in that culture and many other cultures want boys. Boys keep the family name going, can inherit wealth, and represent his father. I think Mariam would have been treated better had she had a boy. Having a son was seen as a wife's accomplishment even though it is the male's sperm that largely decides the gender of a baby. I think Rasheed is abusive despite having a baby boy or girl. He is a misogynist: having a girl just makes him meaner.

Why does Rasheed want a boy?

he wants a son because his son died from drowing in a lake when rasheed was drunk