OG13th 两道数学题请教大牛们

bici

首先是155题，
if y is the smallest positive integer such that 3150 multiplied by y is the square of an integer, then y must be
(A) 2   (B)5   (C)6  (D)7   (E)14

218题
List T consists of 30 positive decimals, none of which is an integer, and the sum of the 30decimals is S. The estimated sum of the 30 decimals , E, is defined as follows. Each decimal in T whose tenths digit is even is rounded up to the nearest integer, and each decimal in T whose tenths digit is odd is rounded down to the nearest integer; E is the sum of the resulting integers. If 1/3 of the decimals in T have a tenths digit that is even, which of the following is a possible value E-S?
I.-16
II.6
III.10
(A) I ONLY
(B) I AND II ONLY
(C) I AND III ONLY
(D) II AND III ONLY
(E) I, II, AND III

冰剑幽蓝

115题：3150*y为一个数的平方，先分解3150,3150=3*3*5*5*2*7，可以看到3*3是3^2,5*5是5^2,所以只要再乘以2和7，也就是14，就可以是一个数的平方，44100为210的平方

218题：设前1/3为X，后2/3为Y。Ex-Sx>10(0.1)=1 (例如15和14.8999）Ex-Sx<10(1)=10 (例如15和14.001)所以 1<Ex-Sx<10
Ey-Sy>20(-1)=-20 (例如15和15.11) Ey-Sy<20(-0.1)=-2(例如15和15.999)所以-20<Ey-Sy<-2
两个相加 -19<(Ex+Ey)-(Sx-Sy)<8