Select the number from among the given option that can replace

Select the number from among the given option that can replace the question mark (?) in the following series.
दिए गए विकल्पों मे से उस संख्या का चयन, कीजिए, जो निम्नलिखित श्रृंखला मे प्रश्न चिह्न (?) को प्रतिस्थापित कर सके ?
9, 5, 6, 10.5, 23, ?

50 60 80 90

Detailed Solution & Logic

Correct Answer:

60

Multiply by 0.5, 1, 1.5, 2 … (increasing by 0.5 each time)
Then add the same number.
$ 9\times 0.5 +0.5 = 5$
$ 5\times 1 +1 = 6 $
$ 6\times 1.5 +1.5 = 10.5$
$ 10.5\times 2 + 2 = 23$
same pattern
$ 23 \times 2.5 + 2.5 = 60$
Answer = 60

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