Question

Find the odd one out from the following series: 5, 10, 20, 40, 100, 150, 200

• A. 10
• B. 40
• C. 100
• D. 150

Hint:

When solving these puzzles, check the numbers in consecutive pairs or small groups instead of only term by term. A consistent multiplying relationship within each group often exposes the one number that does not belong.

Answer 1

The Correct Option is D

The given series is 5, 10, 20, 40, 100, 150, 200. To find the odd one out, let's examine the pattern:

• 5 to 10: multiplied by 2
• 10 to 20: multiplied by 2
• 20 to 40: multiplied by 2
• 40 to 100: here, it breaks the pattern of multiplication by 2. Instead, it's multiplied by 2.5
• 100 to 150: seems arbitrary
• 150 to 200: addition of 50

To maintain a consistent pattern, each term should ideally follow a consistent multiplication rule. The sudden changes at 150 indicate it doesn't fit this sequence behaviorally. Given this, the odd number out is 150.

Answer 2

Concept:

• Instead of comparing every term to the one right before it, group the numbers in the series into consecutive pairs and check whether a consistent relationship holds within each pair.
• A term that cannot be matched into any such pair, while every other number fits neatly into one, is the term that does not belong.

Step 1: Group the seven numbers into consecutive pairs.
$(5, 10), \ (20, 40), \ (100, 150), \ 200$

Step 2: Check the relationship inside each pair.
$10 = 2 \times 5$, $\ 40 = 2 \times 20$, both pairs show the second number is exactly double the first.
$150 = 1.5 \times 100$, this pair does not follow the same doubling relationship.

Step 3: Re-pair using the leftover number to check consistency.
$(100, 200)$ gives $200 = 2 \times 100$, which fits the doubling relationship perfectly.
This leaves 150 without a matching partner that doubles into it or out of it.

Final Answer: $150$