[問題]GWD 10-30

[cimim]

Q30:
Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she
buy?
(1) She bought $4.40 worth of stamps.
(2) She bought an equal number of $0.15 stamps and $0.29 stamps.
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.

答案A WHY????

[yak167]

設0.15的買X張, 0.29的買Y張 ( x>0,Y>0, X Y皆為整數)
條件1
0.15X+0.29Y=4.40
只有Y=10=X時, X Y才有解,
所以(1)就充分, 選A

[cimim]

設0.15的買X張, 0.29的買Y張 ( x>0,Y>0, X Y皆為整數)
條件1
0.15X+0.29Y=4.40
只有Y=10=X時, X Y才有解,
所以(1)就充分, 選A

thx~