Question

The 20th term of the sequence 1, 4, 7, 10, ... is equal to

• A. 56
• B. 66
• C. 68
• D. 58

Hint:

Use $a_n = a + (n-1)d$ directly for nth term of an A.P.

Answer 1

The Correct Option is D

Concept: This is an arithmetic progression (A.P.). Formula: \[ a_n = a + (n-1)d \] Explanation: First term $a = 1$ Common difference $d = 3$ $n = 20$ \[ a_{20} = 1 + (20 - 1) \times 3 \] \[ = 1 + 57 = 58 \]