Q4·CSAT · Prelims 2022
Finding the next term in a decimal multiplier sequence
ReasoningNumber SeriesFactual single● Medium
Question
What is the value of X in the sequence 20, 10, 10, 15, 30, 75, X?
Options
a
105
b
120
c
150
dAnswer
225
Explanation
Determine the multiplier linking each consecutive term: 20 × 0.5 = 10 10 × 1 = 10 10 × 1.5 = 15 15 × 2 = 30 30 × 2.5 = 75
The sequence is generated by multiplying the previous term by a factor that increases by exactly ⟨MATH⟩0.5⟨/MATH⟩ at each step. The next multiplier must be 3.0. Calculate X: 75 × 3 = 225.
If a number sequence drops by half and then steadily rises, the operational pattern is almost universally an escalating fractional multiplier starting at × 0.5.
Answer: (d).
Question details
Year
2022
Paper
CSAT
Question
Q4
Section
Logical & Analytical Reasoning
Sub-topic
Number Series
Type
Factual single
Difficulty
Medium
Source hint
Sequence 20, 10, 10, 15, 30, 75, X
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