Question

23/81 + 43/9 explain me​

Answer 1

Answer:

At first glance, we could say 43 doesn't belong because it is not a square number (that means there is no n that n*n is our number): 9 = 3^2, 16 = 4^2, 25 = 5^2. But as any list, there is no a defined pattern, there are as many patterns as we want to discover! I could say 9 is the number which doesn't belong. A simple reason would be "Because it only has one digit". I think, in fact, 9 is the number doesn't belong, but for another reason: All the digits of 16, 25 and 43 sums to 7. 1+6 = 2+5 = 4+3 = 7. This is a nice excercise to show how can, in the same sequence, be different patterns. This is a problem in cryptography, for example.