GRE Questions

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The given number series is 

3, 5, 8, 15, 28, 51, ?

Here the pattern it follows is

3

3 + 2 = 5 ( add prime number less than 3 i.e, 2)

5 + 3 = 8 (3 is prime number less than 5)

8 + 7 = 15 (7 is prime number less than 8)

15 + 13 = 28 (13 is prime number less than 15)

28 + 23 = 51 (23 is prime number less than 28)

51 + 47 = 98 (47 is prime number less than 51)

Hence, the next number in the given number series is 98.

A person or animal must take in oxygen for respiration to occur. A mouth (choice a) is not essential because breathing can occur through the nose. Choices b and d are clearly not essential and can be ruled out.

The given number series follows a pattern that,

9

9 x 0.5 + 0.5 = 5

5 x 1 + 1 = 6

6 x 2 + 2 = 14

14 x 4 + 4 = 60 (not equals to 56)

60 x 8 + 8 = 488.

Hence, the odd one in the given number series is 56.

Since both the premises are universal and one premise is negative, the conclusion must be universal negative. Also, the conclusion should not contain the middle term. So, 1 follows.

However, 2 is the converse of the second premise and thus it also holds.