下面无忧小编为大家总结了gre猴哥数学难题。gre数学考试中也会出现一些难题，对gre数学考试最有效的方法就是多练习，把数学基础知识记牢，这样才能在考试中对答如流。

　　11. In the equation above, k, r, s, t, and v represent positive numbers. Multiplying which one of these numbers by 2 will reduce the value of n to 1/2 of its present value?