[求助]两个数学问题 谢谢！

summerviolal

1.If 10⁵⁰ – 74 is written as an integer in base 10 notation, what is the sum of the digits in that integer?

A.      424

B.      433

C.      440

D.     449

E.      467                      答案是C          10 notation这个是什么意思啊？

2.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.          答案是D 为什么呢？

谢谢大家！！