Which of the following #'s is different from the others and why? 100, 300, 400, 900, 81, 25, 3600?

Answer 1

81 is not divisible by 5

Answer 2

300 is different. All of the other numbers are products of a number multiplied by itself. 60x60=3600, 5x5=25

Answer 3

300 because it's not a perfect square,
81 because it's not divisible by 5.

Answer 4

300 because it is the only one that is not the square of another number

100 = 10^2
400 = 20^2
900 = 30^2
81 = 9^2
25 = 5^2
3600 = 60^2

Answer 5

They're all different from the others in one way or another:

100 because it's the only one that is a standard denomination of the American dollar
300 because it's not a square number
400 because it's the only one whose digits add up to an even number
900 because it's the only one that signifies a toll call when used as an area code
81 because it's the only one not divisible by 5
25 because it's the only one I could count up to without getting really bored
3600 because it's pronounced with more than three syllables

Answer 6

300 is not a square of any other number
100 = 10 squared
400 = 20
900 = 30
81 = 9
25 = 5
3600 = 60

Answer 7

81 & 25 because they do not end in double zeros and they are they only ones under 100.