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📐 Mathematics  ·  Sequences and Series  ·  JEE

Insert 3 arithmetic means between 5 and 21.

Answer: 9, 13, 17.

  • A 9, 13, 17
  • B 8, 12, 16
  • C 10, 14, 18
  • D 8, 13, 17

Correct answer: A. 9, 13, 17

Explanation: 5 numbers in AP: 5, A, B, C, 21. d = (21-5)/4 = 4. Means: 9, 13, 17.

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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