---

Explanation: 

To calculate how much Juan initially paid for the car we need to know the final price and the margins made by both Juan and Alberto.
Statement 1 gives us both the final sale price and the margin made by Juan. Therefore Statement 1 by itself is not sufficient.
Statement 2 gives us only the margin made by Alberto. Therefore Statement 2 by itself is not sufficient.
Both statements together do give us all of the information we need.

Option C is the correct answer.

---

Explanation: 

To answer the question we need to know the percentage of Jane’s salary with respect to Mandy’s salary.
The first statement alone is not sufficient as it only gives the percentage of Jane’s salary with respect to Mandy’s salary.
The second statement alone is not sufficient as it only gives the percentage of Sally’s salary with respect to Mandy’s salary.
The first statement tells us that, if Mandy earns $100 then Jane will earn $80
The second statement tells us that, if Mandy earns $100 then Sally will earn $120
Using both statements together, we can say that Jane earns 80/120 or 66% of
Mandy’s salary.

Option C is the correct answer.
Note that you do not need to actually calculate the result – only to deduce that you need both pieces of information to do so.

---

Explanation: 

The estimate assumes that: The ratio of copies to readers is the same for ‘Hello’ as for ‘OK’ magazine.
The ratio of copies to readers for ‘OK’ magazine is one copy to every three or four readers. In order for ‘Hello’ magazine, with a circulation of 500,000 copies, to be read by 1.5 to 2 million readers each copy would need to be read by three or four people.

Option B is correct.

---

Explanation :

We need to know the number of bottles in a crate and the selling price of a bottle to know the relationship between the cost and the selling prices of a bottle.
The first statement alone is not sufficient to answer the question as it gives the selling price of a bottle, but the number of bottles per crate is not known.
The second statement alone is not sufficient. The cost of a bottle can be obtained, but the selling price of each bottle is not known.
Combining the two statements, the selling price of a bottle can be obtained from the first statement and the cost per bottle is known from the main question and the second statement. Therefore both the statements together are sufficient to answer the question.
Option C is the correct answer.

---

Explanation: 

On the basis of the given information, you can construct the following:
Princeton > Duke > Yale > Harvard
Cornell > Duke > Yale > Harvard
Princeton = Stanford > Cornell > Duke > Yale > Harvard
Stanford > Princeton > Cornell > Duke > Yale > Harvard
Therefore Duke is now in fourth place.
Option C is the correct answer.