Question

20 AMs are inserted between 2 and 86. The ${19}^{th}$ AM is:

• A. 78
• B. 84
• C. 82
• D. 80

Answer 1

The correct option is A 78

Here 2 is the first term and 86 is the ${22}^{nd}$ term of AP
So, 86 = 2 + (21)d
21d = 84
$\Rightarrow d=4$
So the series is 2,6,10,14,......,82,86

${19}^{th}AM={20}^{th}$ term = 2 + (19)d = 78