SAT questions I did not understand
Can someone give me an explanation for Q1? I am still confused.
In a supermarket, Shakira bought 5 items from aisles 1 through 7, inclusive, and 7 items from aisles 4 through 10, inclusive. Which of the following could be the total number of items that Shakira bought?
A. II only
B. I and II only
C. I and III only
D. II and III only
E. I, II, and III
A purchase from aisles 4 through 7, inclusive, would count in both Shakira’s purchases from aisles 1 through 7, inclusive, and those from aisles 4 through 10, inclusive. So, for example, she could have bought as few as 7 items total: say 5 items from aisle 6 and 2 from aisle 9. Or the total could be as high as 12: say 5 items from aisle 1 and 7 from aisle 10. Any total number of items between 7 and 12 is also possible. In particular, Shakira could have bought 9 items total (for example, 2 items from aisle 1, 3 from aisle 6, and 4 from aisle 10), 10 items total (for example, 3 items from aisle 1, 2 from aisle 6, and 5 from aisle 10), or 11 items total (for example, 4 items from aisle 1, 1 from aisle 6, and 6 from aisle 10). Therefore, the correct answer is I, II, and III.
Q2. Maria is 6 times as old as Tina. In 20 years, Maria will be twice as old as Tina. How old is Maria now?
( I'm recalling this from memory. Correct me if you've seen a problem like this before and this one doesn't make sense.)
Q3. Let T be the sum of numbers 1 to 51 and let Q be the sym of numbers 51 - 100. What is Q-T?
(Same thing, I'm recalling this from memory. Correct me if i'm wrong.)
At Central High School, the math club has 15 members and the chess club has 12 members. If a total of 13 students belong to only one of the two clubs, how many students belong to both clubs?