CMA Foundation · Fundamentals of Business Mathematics and Statistics · Arithmetic Progression and Geometric Progression
In an arithmetic progression the 4th term is 17 and the 9th term is 42. What is the 15th term?
The 15th term is 72. The difference between the 9th and 4th terms is 25 over 5 steps, so the common difference is 5. The first term is 17 - 15 = 2, and the 15th term is 2 + 14 x 5 = 72.
- A72Correct
- B70
- C75
- D67
Explanation
5d = 42 - 17 = 25, so d = 5. a + 3d = 17 gives a = 2. The 15th term = 2 + 14 x 5 = 72. Option 70 comes from using 13d instead of 14d.
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