Question

Insert the missing number:
4, 9, 20, 43, 90, ___

• A. 185
• B. 172
• C. 179
• D. 165
• E. None of the above

Answer 1

The correct option is A 185

The pattern is
9 = 2 $\times$ 4 + 1
20 = 2 $\times$ 9 +2
43 = 2 $\times$ 20 + 3
90 = 2 x 43 $\times$ 4
$\therefore$ ? should be 2 $\times$ 90 + 5 = 185.