Question

which are natural numbers: -3, 0, 2, 8.99, square root of 7, square root of 64, 9 1/2, -20/47, 1.2525525552

Answer 1

Does your teach consider zero to be a natural number ?

http://en.wikipedia.org/wiki/Natural_number

There is no universal agreement about whether to include zero in the set of natural numbers: some define the natural numbers to be the positive integers {1, 2, 3, ...}, while for others the term designates the non-negative integers {0, 1, 2, 3, ...}. The former definition is the traditional one, with the latter definition first appearing in the 19th century. Some authors use the term natural number to exclude zero and whole number to include it; others use whole number in a way that excludes zero, or in a way that includes both zero and the negative integers.

Answer 2

-3 : no - it's negative, so not natural
0 : depends on your teacher's definition
2 : yes - natural
8.99 : no - not whole number
square root of 7 : no - not a whole number
square root of 64 : yes - coz 8 is a natural number
9 1/2 : no - not a whole number
-20/47 : no - it's negative and it's not a whole number
1.2525525552 : no - not a whole number

Answer 3

which are rational numbers: 14, 0, 50, 2.84, square root of 15, square root of 1, 8 1/6, -17/43, 1.161661666