标题: OG13th 两道数学题请教大牛们 [打印本页] 作者: bici 时间: 2012-9-19 22:23 标题: OG13th 两道数学题请教大牛们 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作者: 冰剑幽蓝 时间: 2012-9-20 22:12
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