GWD16的两道数学题

jiyiflora

    

请高人帮我指点一下

19这题我看不懂题目  

Q19:

    

How
many 4-digit positive integers are there in which all 4 digits are even?

    

 

    

A.   
625

    

B.    
600

    

C.    
500

    

D.   
400

    

E.    
256

    

Answer:

    

21题答案选D,我看条件1不能得出来答案啊

Q21:

    

Color
X ink is created by blending red, blue, green, and yellow inks in the
ratio 6 : 5 : 2 : 2.  What is the number
of liters of green ink that was used to create a certain batch of color X
ink?

    

(1)   The amount of red ink used to create the
batch is 2 liters more than the amount of blue ink used to create the batch.

    

(2)     The
batch consists of 30 liters of color X ink.

    

                  

    

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.

frankmfg

Q21.设blue为x，则red为x+2
6 : 5=x+2：x
得x=10

再设green为y
blue：green=5 : 2
5：2=10：y
y=4

frankmfg

19.4（2，4，6，8）x 5 （0,2，4，6，8）x 5 x 5=500

Lofire

Q19：让你求4位数的整数中，四个数位（个十百千）都是偶数的整数有多少个？

分析：共有0，2，4，6，8 五个数字可以组成这样的偶数；为保证‘千位’不为0，我们在2468中任选一个作为千位有4种选择，接下来‘个十百’位都可以是02468中任意一个，即各有5种选择。因此，总共有4*5*5*5=500种组合，即有500个这样的4位整数。选C。

Q21：如果各成分比例固定，那么，1）知道比例之间的差距；2）知道总量 都可以推出各成分的量。选D。

jiyiflora

谢谢各位。