Question

In the following number series, a wrong number is given. Find the wrong number.
21, 455, 445, 465, 435, 485, 415, 475

• A. 475
• B. 465
• C. 435
• D. 455
• E. 445

Answer 1

The correct option is A 475

Series formed by numbers at odd and even places respectively are:
455, 465, 485, 475 ...(1)
and,
445, 435, 415 ...(2)
The difference between successive terms of I are:
10, 20, - 10
and of 2 are
- 10,-20
- 10 in (1) is abnormal. It should be 30.
$\therefore$ 475 is wrong and should be replaced by 485 + 30 = 515.