Explanation

Question 4: The private : public ratio in 1990 was about \(\frac{13}{5}\). Setting the ratios equal for the two years (setting up a proportion) gives you: \(\frac{13}{5}=\frac{x}{11000}\). The private cost is approximately $29,000, so the answer is choice C.

Question 5: The cost increases from about $6,000 to $22,000. Use the percent change formula to find the percent increase: \(\frac{16000}{6000}*100= 267%\), so the answer is choice D.

Question 6: The average cost of a private university in 1995 was $17,000, and the cost in 2000 was $22,000, as you discovered in the previous question. The increase over the 5-year period was $5,000. If the average cost increased at a constant rate, then the increase was $1,000 per year.
The 3-year increase from 1995 to 1998 was therefore $3,000, putting the average cost for a private university at $20,000 in 1998. To find the total cost for that year, multiply the average cost per student times the number of students: ($20,000)(2.5 million) = $50 billion. Similarly, in 1990, the total dollar amount spent on private universities was ($13,000)(2 million) = $26 billion. The billions cancel out of the percent change formula, giving you \(\frac{24}{26}*100 = 92%\), which is the closest to choice E.