• # question_answer On the eve of Holi festival, a group of 15 friends greeted every other friend by sending greeting cards. Find the number of cards purchased by group. A)  156B)  144C)  210D)  320

There being 15 friends in the group, each friend must have purchased $(15-1)$ i.e 14 cards for sending greeting to rest of his 14 friends. Thus total number of cards Purchased by all the friends together is $15\times 14$ i.e. 210.