Halachos of Daily Living

To be
counted towards the one hundred 
brachos, must one personally recite the bracha, or is
it sufficient to respond amen to another person’s 
bracha?

It depends on the bracha.

If the bracha is
obligatory
 (such as Kiddush or Hamotzi) and a person fulfills the requirement to
recite the bracha by
hearing it from another, the bracha can be included in a person’s daily tally
of the one hundred brachos obligation.

If a bracha is non-obligatory and a person hears the bracha from
another and answers amen (such as a bracha on an apple that
another party is reciting), it does not count towards the one hundred brachos.