3月5号,一战北京,700,Q50V34, 大量jj

Howto

SC温室效应是不是这个题啊

GWD3-Q19:

Possible long-term consequences of the “greenhouse effect,” the gradual warming of the Earth’s climate, may include melting the polar ice caps and a rising sea level.

1. may include melting the polar ice caps and a rising sea level

2. may include the melting of polar ice caps and the rising sea level

3. may include polar ice caps that are melting and sea levels that are rising

4. include melting the polar ice caps and sea levels that are rising

5. include melting of the polar ice caps and a rise in sea level

请JJ主人看看

cypress__ye

lz对SC实战的看法简直是及时雨，我这两天刚准备反复看OG，看来要转移了

thank you very much indeed

gmat4wk

If 1^ 2 + 2^ 2+ ... n^2  is a multiple of 4, sum of square of all odd terms is also a multiple of 4. This is because the sum of square of all even numbers is a multiple of 4 regardless of n.

for any integer k,  (2k-1)^2 = (2k)(2k-2)-1=4k(k-1)-1
therefore 1^2 + 3^2+ ... (2k+1)^2 is a multiple of 4 only if k is a multiple of 4.

n= 104, k= 52, YES!
n=105, 106, k=53, NO!

rogerleex

题外总结：任意2个连续奇数相加，能被4整除，任意4个连续奇数平方相加，能被4整除

n=2k+1，m=2k+3

N=4k+1，N1=4K+5,N3=4k+9, N4=4k+13

sacrylin

补充27楼

任何一个奇数可以假设为 p=2×n+1;其平方=4n*n+4n+1;所以任何一个奇数平方被四整除都余一。

由于偶数平方肯定能被4整除，所以只需看奇数情况；

105和106都有53个奇数，所以其余了53个一，其平方和不能被四整除；104有52个奇数，52/4=13，所以选104；

另外一点个人感受：gmat的出题者从来都不会出一道计算量夸张的题，有些题表面计算量吓人，但是总是有技巧和方法，甚至都不要用到我们高中的公式，而需要我们来个脑筋急转弯。