Paper 1 · Mathematical Reasoning and Aptitude
UGC NET December 2022 (16.03.2023) Shift-I (Psychology)
The sum of 15 terms of an arithmetic progression is 600 and the common difference between consecutive terms is 5. Find the first term of the series.
A5 ✓ Correct
B7
C8
D9
Correct answer: (A) 5 — The answer is 5.
Explanation
★The answer is 5.
★The sum of n terms is n by 2 times twice the first term plus n minus 1 times the difference.
★Here 600 equals 15 by 2 times twice a plus 14 times 5.
★So 80 equals twice a plus 70.
★Then twice a is 10.
★So the first term a is 5.
★So the answer is 5.
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