series

Question

Look at this series: F2, __, D8, C16, B32, ... What number should fill the blank?

Answer 1

Here the letters decrease by 1; the numbers are multiplied by 2.

$(F-1)(2\times2)=E4$

$(E-1)(4\times2)=D8$

$(D-1)(8\times2)=C16$

$(C-1)(16\times2)=B32$

Answer 2

Alphabets are written in the reverse pattern, the number is in $2^n,n=1,2,3,4….$ that is;

• $F2\rightarrow F 2^1$
• $E4\rightarrow (F-1) 2^2$
• $D8\rightarrow (E-1)2^3$
• $C16\rightarrow (D-1)2^4$
• $B32\rightarrow (C-1)2^5$

So the missing term is $E4.$