[求助]求助3道数学题

这是GWD最新13套中的第11套，没想到，这套的答案是“面目全非啊”，每一个对的，明显是答案给错了。；（  咳，白做了，没有答案可对。

但有几道题不会，特上来请教。

GWD 11

Q10: (不会做)

A certain quantity is measured on two different scales, the R-scale and the S-scale, that are related linearly. 
Measurements on the R-scale of
6 and 24 correspond to measurements on the S-scale
of 30 and 60, respectively.  What
measurement on the R-scale
corresponds to a measurement of 100 on the S-scale?

A.    20

B.     36

C.     48

D.    60

E.     84

Q25:

If the sequence x₁,
x_2, x_{3, …,} x_n,
… is such that x₁  = 3 and x_n+1
        = 2x_n
– 1 for n ≥ 1, then x₂₀ – x₁₉ =

A.    2¹⁹

B.     2²⁰

C.     2²¹

D.    2²⁰
- 1

E.     2²¹
- 1

Answer:  我选 A，不确定

Q32:

If n is a positive
integer, what is the value of the hundreds digit of 30ⁿ?

(1)
          30ⁿ > 1,000

(2)
          n is a multiple of 3.

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.