How to Bound Equations that Get Larger on the ACT

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Problem:

In the equation r = 4/(2 + k), k represents a positive integer. As k gets larger without bound, the value of r:

F. gets closer and closer to 4.
G. gets closer and closer to 2.
H. gets closer and closer to 0.
J. remains constant.
K. gets larger and larger 

Answer:

Answer is H.

As k gets larger and larger without bound, the expression 4/(2+k) becomes 4 divided by an increasingly large number. For example, think about the trend between the following fractions:

4/100,
4/10,000,
4/1,000,000, ...

Looking at it this way, you can see that the expression for r gets closer and closer to zero.