Question

Find the missing numbers

$8,7,16,5,32,3,64,1,128,(?)$

• A. $18$
• B. $13$
• C. $-1$
• D. $3$

Answer 1

Answer: (C)

$-1$

The given series 8, 7, 16, 5, 32, 3, 64, 1, 128, (?) is a combination of two series.
1st series: 8, 16, 32, 64, 128 2nd series: 7, 5, 3, 1, (?)
In the 1st series. each term get doubled from its previous term.
In the 2nd series, each term is decreases by $2$ in each step.
Clearly, 1 - 2 = -1
Hence, option (C) is the correct answer.