请教几个数学题

1. If each term in the sum A1+A2+...+An is either 7 or 77 and the sum equals 350, which of the following could be equal to n?

38/39/40/41/42

2. If x, y and z are integers greater than 1, what is the value of x+y+z?

(1) xyz=70

(2)x/(yz)=7/10

答案选A    烦请各位分析解答过程了...

1. If each term in the sum A1+A2+...+An is either 7 or 77 and the sum equals 350, which of the following could be equal to n?

38/39/40/41/42

350里一共有50个7，77有11个7，

所以！350里有39个7和1个77，答案选40，而非39~~

2. If x, y and z are integers greater than 1, what is the value of x+y+z?

(1) xyz=70

(2)x/(yz)=7/10

（1）因为X，Y，Z都是整数，所以XYZ=2*5*7

（2）只知道他们之间的比例关系，不知道确切的数