While researching the reasons for the large cross-cultural differences, Stevenson and his colleagues observed that more than of total classroom time in the first grade was spent on math instruction in Japan, compared with only of the time in the U. S. first-grade classrooms.

one fourth, one tenth

Explanation:cross cultural learning describes the way students learn more about their own culture and the culture of other people. It makes them to have a thorough knowledge of culture, traditions norms and beliefs of different people.the learning of culture has it's significance in the life of a child because it helps them prepare for the outside world. It gives them insight, understand and knowledge. Most times it is difficult learning the culture of others especially their language, way of life but in the long run, it makes you to be knowledgeable about other cultures and how to relate with people of other cultural background.

explanation:

may i ask what challenges?

well it depends i think people around the world are coming around to gay marriage. but if you are talking abortion then wow, so much to talk about. such as men thinking they have the right to choose if women can, the fact there are health concerns if the women can't get one, and many more arguments to discuss. so i would definitely say abortion would be a much more interesting topic.