Test Index

Number series coding and Decoding and odd man out

Question : 31 of 51

Marks: +1, -0

15,21,63,81,69

Solution:

Concept:

Identify the number that does not share a common property with the others.

Explanation:

All numbers are multiples of 3.

But 81 is the only perfect power of 3 (

3^4

), while the others have an additional prime factor:

15 = 3 \times 5

21 = 3 \times 7

63 = 3^2 \times 7

69 = 3 \times 23

Thus, 81 is the odd one out.

Answer:

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