SAT数学备考经典模拟题训练24

>>SAT数学模拟题：SAT数学备考经典模拟题训练24

>>SAT考试辅导

7. If y ¤ x = y2x for all positive integers, then (3 ¤ 4) ¤ 2 =

A. 38

B. 312

C. 316

D. 324

E. 332

8. The first term in a sequence is 1 and the second term is 5. From the third term on each term is the average (arithmetic mean) of all preceding terms. What is the 25th term in the sequence?

A. 2.5

B. 3

C. 5

D. 25

E. 50

7.Correct Answer: E

Explanation:

The strange sign tells us what operation to carry out on x and y

Carry out the same procedure on 3 and 4 first. So 38 is the result.

Now carry out the procedure on 38 and 2. So (38)4 is the result, which is equivalent to 332

8.Correct Answer: B

Explanation:

Start constructing the sequence until you see the pattern

1...5...(average of 1 and 5 = 3)...(average of 1, 5, and 3 = 3)...(average of 1,5,3 and 3 = 3)

now you can see that all subsequent terms will be 3

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