Question Bank • QB_GA_ASA_001
NAT • 2 Marks
Section 8: General Aptitude
Analytical & Spatial Aptitude
Subtopic: Logic Deduction & Pattern Recognition
Question Statement:
Find the next missing number in the numerical series: $3, 8, 18, 38, 78, \underline{\hspace{1.5cm}}$ (answer in integer).
Step-by-Step Solution & Explanation
1. Examine the difference pattern between consecutive terms:
• $8 - 3 = 5$
• $18 - 8 = 10$
• $38 - 18 = 20$
• $78 - 38 = 40$
2. The successive differences double each time: $5, 10, 20, 40, 80$.
3. Next term $= 78 + 80 = 158$.
(Alternatively, each term follows the recurrence relation $T_{n} = 2 \times T_{n-1} + 2$, giving $2 \times 78 + 2 = 158$).
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