A young girl counted in the following way on the fingers of her left hand. She started calling the thumb 1, the index finger 2, middle finger 3, ring finger 4, little finger 5, then reversed direction, calling the ring finger 6, middle finger 7, index finger 8, thumb 9 and then back to the index finger for 10, middle finger for 11, and so on. She counted upto 1994. She ended on her

A. thumb

B. index finger

C. middle finger

D. ring finger

Answer: Option B

Solution(By Examveda Team)

Number of thumbs = 1, 9, 17, 25, .....
This is an AP in which a = 1 and d = (9 - 1) = 8
∴ T_n = a + (n - 1) d
        = 1 + (n - 1) 8
        = (8n - 7)
∵ 8n - 7 = 1994
⇒ 8n = 2001
⇒ n = 250
T₂₅₀ = 1 + (250 - 1) 8
        = 1 + 249 × 8
        = 1993
So, 1993 lies on thumb and 1994 on index finger.