求助几道GWD数学题，帮我解答一下，谢谢！！！

敬蕊will

The sides of a square region, measured to the nearest centimeters, are 6 centimeters long.  The least possible value of the actual area of the square region is

 

A.     36.00 sq cm  B.     35.00 sq cm  C.     33.75 sq cm   D.     30.25 sq cm   E.      25.00 sq cm

本题，我不明白它的题意是什么意思？答案是D

For all integers x and y, the operation D is defined by xDy = (x+2)² + (y+3)².  What is the value of integer t?

(1)     t D 2 = 74

(2)     2 D t = 80

                  

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

本题答案是C,但我认为是E，因为t的值是不确定的

Before a certain tire is used, 40 percent of its total weight consists of tread.  If during a lifetime of use, 50 percent, by weight, of the tire’s tread is lost and no other parts of the tire is lost, what per cent of the tire’s total remaining weight consists of the remaining tread?

 

A.   55%

B.   20%

C.   25%

D.      30%

E.       35%

本题也是不明白题意，绕来绕去的，能帮我分析一下题意吗？谢谢！答案是C

What is the greatest common factor of the positive integers j and k?

(1)     k = j + 1

(2)     jk is divisible by 5.

                  

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.

本题一点思路都没有，希望指点一下！谢谢！答案是A

One kilogram of a certain coffee blend consists of x kilogram of type I coffee and y kilogram of type II coffee.  The cost of the blend is C dollars per kilogram, where C = 6.5x + 8.5y.  Is x < 0.8?

(1)     y > 0.15

(2)     C ≥ 7.30

                  

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.

像这样的题，我总是搞不定，希望帮我分析一下！答案是B

是不是有点多？回答一个也好，急切等待分析，谢谢！

敬蕊will

我自己顶一下，真的想知道答案，谢谢！

敬蕊will

十分的感谢啊！都明白了！谢谢！

敬蕊will

还差最后一道题，谢谢啦！！！