If the given expression (11n + 1) is for numbers in a series (taking n = 1, 2, 3, 4…… in order).
Which of the following numbers does not belong to the given series?
1000
For the given series 11n + 1, if we take n = 1, 2, 3, 4……. (in order).
We get the numbers 12, 23, 34, 45, 56, 67, 78, 89, 100…..
All these numbers leave remainder 1 when divided by 11.
When we divide 1000 by 11 the remainder is 10 and not 1.
∴ 1000 does not belong to the given series.