NIMCET 2010
Which should be the next two numbers in the series 28, 25, 5, 21, 18, 5, 14, ?, ?
Answer (Detailed Solution Below)View answer ▾Hide ▴
Answer: Option A — 11, 5
Detailed Solution
Leaving out the 5s: 28, 25, 21, 18, 14 fall by 3, 4, 3, 4.
A 5 is inserted after every two of these terms.
Next: 14 − 3 = 11, then the inserted 5, giving 11, 5.
✓ Check
The full series 28, 25, 5, 21, 18, 5, 14, 11, 5 keeps the pattern 'two terms, then 5'.⚠ Common trap
(C) 11, 8 continues the falling numbers but forgets the 5 that follows every pair.Quick tip
Falls of 3 and 4 alternately, with a 5 after every pair.
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Series — Preparation
This question tests your understanding of Series, a key topic in the Logical Reasoning section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
Series questions give a sequence of numbers, letters or a mix of both, and ask you to find the next term, a missing term, or the wrong term. This topic covers number series (based on differences, squares and cubes, multiplication, or mixed operations), letter series, alphanumeric series, and repeating letter patterns. Start by checking the differences between consecutive terms. If those don't show a pattern, check the second differences, ratios, squares and cubes nearby, or whether two separate series alternate. For letter series, convert letters to their alphabet positions and look for the number pattern. With practice, recognising common patterns becomes quick and these questions become reliable marks. Practise the series questions below, each with a step-by-step solution that shows the pattern.