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Railways PYQCBT 1 2016

RRB NTPC · Question 39

What is the average of first 30 multiples of 9?

  1. 142

  2. 138.5

  3. 139.5

  4. 143.5

Show answer & explanation

Answer: (C) 139.5

Explanation

The first 30 multiples of 9 are 9 × 1 to 9 × 30. Their average = 9 × (1 + 30)/2 = 9 × 15.5 = 139.5.