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Number series coding and Decoding and odd man out

Question : 16 of 51

Marks: +1, -0

1,5,14,30,51,55,91

Solution:

Concept:

Identify the number that does not follow the pattern of sum of squares of natural numbers.

Explanation:

The correct pattern is sums of squares:

1=1^2

5=1^2+2^2

14=1^2+2^2+3^2

30=1^2+2^2+3^2+4^2

55=1^2+2^2+3^2+4^2+5^2

91=1^2+2^2+3^2+4^2+5^2+6^2

The given series is

1,5,14,30,51,55,91

Here

51

breaks the pattern (should be

55

), and

55

appears later in its correct place.

Thus

51

is the odd one out.

Answer:

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