Question

Which one of these numbers is not like the others 25,16,49,63,81

Answer 1

16 is the only even and the rest are ods

Answer 2

1 way: You can see that

• $25=5^2;$
• $16=4^2;$
• $49=7^2;$
• $81=9^2;$
• 63 is not a perfect square.

Answer: 63 is not like the others.

2 way:

• numbers 25, 63, 49 and 81 are odd numbers;
• number 16 is even number.

Answer: 16 is not like the others.