请教大家啊

trialybt

Q5:

Is x > k?

(1)     2^x • 2^k = 4

(2)     9^x • 3^k = 81

                  

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.

x+k=2, x+k=1

算不出来啊？答案给的是C

这是狒狒数学三十套上的题，请问哪里有详细的解题啊？谢谢啊！

mymengming

x+k=2, x+k=4

trialybt

这也算不出来啊？

trialybt

If 10⁵⁰ – 74 is written as an integer in base 10 notation, what is the sum of the digits in that integer?

 

A.      424

B.      433

C.      440

D.     449

E.      467

那位好心人能解释一下这题的意思吗？谢谢啊～！

Alice520

(2)     9^x • 3^k = 81

这个式子是得 2x+k=4啊

所以x k都可得

就选c咯~

这个式子是得 2x+k=4啊

所以x k都可得

就选c咯~

Alice520

If 10⁵⁰ – 74 is written as an integer in base 10 notation, what is the sum of the digits in that integer?

A.      424

B.      433

C.      440

D.     449

E.      467

100-74=26  10^{50_100 是48个9和两个0}

^{所以2+6+48*9=440}

^呵呵

trialybt

谢谢，一时没转过来，一直在想是3+x+k=4

trialybt

实在是太感谢，你解释的太清楚了，我就不客气了，还有一题也没做出来，是什么方法没对。谢谢啊！

Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y.  At these rates, if the two machines together produce 5/4 w widgets in 3 days, how many days would it take machine X alone to produce 2w widgets?

 

A.      4

B.      6

C.      8

D.     10

E.      12

E

Alice520

以下是引用trialybt在2009-2-6 14:30:00的发言：

实在是太感谢，你解释的太清楚了，我就不客气了，还有一题也没做出来，是什么方法没对。谢谢啊！

Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y.  At these rates, if the two machines together produce 5/4 w widgets in 3 days, how many days would it take machine X alone to produce 2w widgets?

A.      4

B.      6

C.      8

D.     10

E.      12

E

不客气 呵呵

设X Y各生产w需要x y天

则 x=y+2

(w/x+w/y)*3=5/4w

解两个方程得 x=6

X生产w用6天 生产2w就用12天啦~ 

trialybt

谢谢，再帮忙解释一下这一道题！严重感谢啊！