请教牛人帮忙解答一下，数学实在是太烂了！跪谢了！

涛涛5中的两道题：

Q33:

Enrollment in City College in 1980 was 83? percent of enrollment in 1990.  What was the percent increase in the college’s enrollment from 1980 to 1990?

A.    10%

B.     16?%

C.     20%

D.    25%

E.     183?%

Q28:

Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day.  If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper B, which of the following expresses r in terms of p?

A.    100p / (125 – p)

B.     150p / (250 – p)

C.     300p / (375 – p)

D.    400p / (500 – p)

E.     500p / (625 – p)

涛涛7：

Q28:

This year Henry will save a certain amount of his income, and he will spend the rest.  Next year Henry will have no income, but for each dollar that he saves this year, he will have 1 + r dollars available to spend.  In terms of r, what fraction of his income should Henry save this year so that next year the amount he was available to spend will be equal to half the amount that he spends this year?

答案为 1/2r+3   这道题基本就没看明白，请牛人指点一下！

Q29:

Leo can buy a certain computer for p₁ dollars in State A, where the sales tax is t₁ percent, or he can buy the same computer for p₂ dollars in State B, where the sales tax is t₂ percent.  Is the total cost of the computer greater in State A than in State B?

(1)     t₁ > t₂

(2)     p₁t₁ > p₂t₂

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.

Q21:

Theater M has 25 rows with 27 seats in each row.  How many of the seats were occupied during a certain show?

(1)   During the show, there was an average (arithmetic mean) of 10 unoccupied seats per row for the front 20 rows.

(2)   During the show, there was an average (arithmetic mean) of 20 unoccupied seats per row for the back 15 rows.

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.

Q16:

For any integer k greater than 1, the symbol k^* denotes the product of all the fractions of the form , where t is an integer between 1 and k, inclusive.  What is the value of ?

答案为1/5