Answer :
Integers and Rationals
All integers are rationals, but not all the rationals are integers
Generally speaking, rationals are fractions like 3/4, 8/3, 10/5
Note the last fraction 10/5 is rational but it also is an integer, because 10/5=2
The other rationals given cannot be divided without remainder
There are real-life situations where we can easily tell between a rational number that cannot be expressed as an integer
We have four situations here:
A: Number of students in a classroom
Since the number of students in a classroom is a magnitude that can be counted, it's impossible that it's a fraction like 8/3. There cannot be 2.6 students in a classroom
Therefore, this option is not correct
B: Score on a math test
Assuming every question in the test is counted as an integer, and there cannot be partial marks (like 3.5 out of 5), this is not a situation where the number can be a non-integer.
This option is not correct.
C: Number of keys in a keyboard
As specified in option A, the number of keys in a keyboard is a countable quantity. You cannot have 5.3 keys.
D: Price of a pencil
We cannot count the price of a pencil. It can be any number integer or not.
For example, the box of 6 pencils cost $4, thus each pencil costs $4/6
This is the correct option
