ChaseDream

标题: GWD27-32 [打印本页]

---

作者: nicboy    时间: 2008-6-26 15:40
标题: GWD27-32

        

Q32:

        

If x³y⁴
= 5,000, is y = 5?

        

(1)
                  y is a positive integer.

        

(2)
                  x is an integer.

        

              

        

A. Statement (1) ALONE
is sufficient, but statement (2) alone is not sufficient.

        

B. Statement (2) ALONE
is sufficient, but statement (1) alone is not sufficient.

        

C. BOTH statements
TOGETHER are sufficient, but NEITHER statement ALONE is
sufficient.

        

D. EACH
statement ALONE is sufficient.

        

E. Statements (1)
and (2) TOGETHER are NOT sufficient.

        

我的问题是为什么是 C呢， A 就足够了吧， 当A是整数的时候，它的4次方也是整数，

---

作者: 喝咖啡的狼    时间: 2008-6-26 18:40

what about x = 1/5000 and y = 5000?

[此贴子已经被作者于2008-6-26 18:52:44编辑过]

---

作者: bth    时间: 2008-6-26 18:53

(1) put y = 1, then x = cube root (5000)

put y = 2, then x = cube root(5000/16) and so on... --> Insuff

(2) put x = 1, y = 5000^1/4
put x = -1, y = - (5000^1/4)

put x = 3, y = (5000/8)^1/4 and so on... --> Insuff

1 & 2 - Together x and y can only be integers and y only positive - Suff

Hence, C

 

---

作者: ConnieC    时间: 2010-8-4 10:47
留爪

---

欢迎光临 ChaseDream (https://forum.chasedream.com/)

Powered by Discuz! X3.3