Correct option 1: 6.5

Analyzing the Number Series Pattern

The given series is 17, 22, 11, 16, 8, 13, ?. We need to find the number that replaces the question mark by identifying the underlying pattern in the series.

Let's examine the relationship between consecutive terms:

• From 17 to 22: We add 5 (17+5=2217+5=22).

• From 22 to 11: We divide by 2 (22÷2=1122÷2=11).

• From 11 to 16: We add 5 (11+5=1611+5=16).

• From 16 to 8: We divide by 2 (16÷2=816÷2=8).

• From 8 to 13: We add 5 (8+5=138+5=13).

It appears there is a repeating pattern of operations: Add 5, then Divide by 2, then Add 5, then Divide by 2, and so on.

Following this pattern, the next operation after adding 5 to get 13 should be dividing by 2.

So, to find the missing number, we perform the next step in the sequence of operations on the last known term (13):

Divide the last term by 2:

Missing number=13÷2 

Missing number=6.5

Therefore, the number that replaces the question mark is 6.5.