Question

Select the number from among the given options that can replace the question mark (?) in the following series. 23, 2, 89, 177, 353, 705

• A. 45
• B. 47
• C. 49
• D. 42

Answer 1

Answer:

A. 45

Let’s look at the pattern:

Series:
23, 2, 89, 177, 353, 705

Observe pattern from 3rd term onwards

89 → 177 → 353 → 705

Check:

• 89 × 2 − 1 = 177

• 177 × 2 − 1 = 353

• 353 × 2 − 1 = 705

So pattern is:
Next term = (previous × 2) − 1

Apply same pattern backward

Let missing term be x:

x × 2 − 1 = 89
⇒ x × 2 = 90
⇒ x = 45

Check earlier consistency

23 → 2 → 45 → 89 works with pattern from 45 onward.

Final Answer: 45