Question

In the following number series, a wrong number is given. out the wrong number.
8, 18, 40, 86, 178, 370, 752

• A. 86
• B. 178
• C. 40
• D. 370
• E. 752

Answer 1

The correct option is B 178

18 = 8 $\times$ 2 + 2 $\times$ 1; 40 = 18 $\times$ 2 + 2 $\times$ 2
86 = 40 $\times$ 2 + 2 $\times$ 3; 178 $\ne$ 86 $\times$ 2 + 2 $\times$ 4
370 $\ne$ 178 $\times$ 2 + 2 $\times$ 5; 752 = 370 $\times$ 2 + 2 $\times$ 6
$\therefore$ 178 is wrong and should be replaced by
2 $\times$ 86 + 2 $\times$ 4 = 180
With this choice 5th place
2 $\times$ 180 + 2 $\times$ 5 = 370
which is according to the pattern.