Question

3 A.M.’s between 3 and 19 are

• A. 7, 11, 15
• B. 4, 6, 10
• C. 6, 10, 14
• D. None of these

Answer 1

Answer: (A)

7, 11, 15

Answer 2

Let $A_{1},A_{2},A_{3}$ be three A.M.’s. Then $3,A_{1},A_{2},A_{3},19$ are in A.P.

⇒ Common difference $d = \frac{19 - 3}{3 + 1} = 4$.Therefore

$A_{1} = 3 + d = 7$, $A_{2} = 3 + 2d = 11$, $A_{3} = 3 + 3d = 15$