GWD22-2,22-19.22-23

Q2:

In planning for a trip, Joan estimated both the distance of the trip, in miles, and her average speed, in miles per hour.  She accurately divided her estimated distance by her estimated average speed to obtain an estimate for the time, in hours, that the trip would take.  Was her estimate within 0.5 hour of the actual time that the trip took?

(1)   Joan’s estimate for the distance was within 5 miles of the actual distance.

(2) Joan’s estimate for her average speed was within 10 miles per hour of her actual average speed.

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.

选E.题没怎么读懂,能帮忙解释一下吗?

Q19:

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

选E

Q20:

If k is an integer and (0.0025)(0.025)(0.00025)×10^k is an integer, what is the least possible value of k?

A.   -12

B.       -6

C.       0

D.   6

E.    12

选E

Q23:

If r and t are positive integers, what is the value of t?

(1)   t^r-1 = 1

(2)   r ¹ 1

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.

选C, 可我觉得t可以等于+1 or -1...