In an arithmetic progression, the 3rd term is 11 and the 7th term is 27. What is the 15th term?
Answer and explanation
Correct answer: A. 59
- Step 1: The general term is a_n = a_1 + (n - 1)*d.
- Step 2: Subtract the 3rd term from the 7th term: a_7 - a_3 = 4*d = 27 - 11 = 16, so d = 4.
- Step 3: Find a_1: a_3 = a_1 + 2*(4) = 11, so a_1 = 3.
- Step 4: Compute a_15 = 3 + 14*(4) = 3 + 56 = 59.
Answer
59.
Why not the others: 55 computes 3 + 134; 63 computes 3 + 154; 51 computes 3 + 12*4.
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