求助]

guyan

求助大虾们几道数学题， 是princeton 模考上的
1.what is the maxmimum capacity , in cups, of a pail that contains only sand and is filled to three-fourths of its capacity?
1)if one cup of sand were added to the pail, it would then be filled to sevevn -eighths of its capacity.
2)if two cups were removed from the pail, it would then be filled to one-hail of its capacity.
答案是D 我不知道怎麽算。
2.five people meet and exchange shakehands, if exactly 3 of the people each shake hands with 3 people, and if 1 person shakes hands with only 1 other person, then what is the least number of handshakes that would have been exchanged.
答案是6， 不知是不是P33算出的。
3 in a survey of parents, exactly 3/4 of the mothers and 9/10 of fathers held full-time jobs, if 40percent of the parents surveyed were women, what percent of the parents did not hold full-time jobs?
干脆不明百！
谢谢谢谢万分感谢！