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📐 Mathematics  ·  Sequences and Series  ·  JEE

In an AP, if 3rd term = 7 and 7th term = 15, find d.

Answer: 2.

  • A 1
  • B 2
  • C 3
  • D 4

Correct answer: B. 2

Explanation: a + 2d = 7 and a + 6d = 15. Subtracting: 4d = 8, d = 2.

Each bar grows by the common difference d=3a1=2a2=5a3=8a4=11d=3

Bar heights for AP 2, 5, 8, 11 with the common difference d=3 marked between consecutive terms.

Concept context

Arithmetic progressions, geometric progressions, and sums

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