GMAT两大数学题求解答

GMAT两大数学题求解答
1.Each participant in a certain study was assigned a sequence of 3 different letters from the set {A,B,C,D,E,F,G,H}.If no sequence was assigned to more than one participant and if 36 of the possible sequences were not assigned,what was the number of participants in the study?(Note,for example,that the sequence A,B,C is different from the sequence C,B,A.)
A.20
B.92
C.300
D.372
E.476
Stations X and Y are connected by two separate,straight,parallel rail lines that are 250 miles long.Train P and train Q simultaneously left Station X and Station Y,respectively,and each train traveled to the other’s point of departure.The two trains passed each other after traveling for 2 hours.When the two trains passed,which train was nearer to its destination?
(1) At the time when the two trains passed,train P had averaged a speed of 70 miles per hour.
(2) Train Q averaged a speed of 55 miles per hour for the entire trip.
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.
第一题答案为C,第二题答案为A.