Answer:
Option 4
Step-by-step explanation:
Let any two real number a and b (no matter +ve, -ve or 0). a ≥ b
The average of them will always lie in between them or be equal(if 0).
Let's prove : According to the statement,
a ≥ (a + b)/2 ≥ b
2a ≥ a + b ≥ 2b
2a ≥ a + b and a + b ≥ 2b
a ≥ b and a ≥ b, as we assumed.
Moreover, as the average exists in between a and b, we have the average (a + b)/2. Similarly, there exists one more average of (a + b)/2 and a or b, which definitely lie between a and b as (a + b)/2 lies there and smaller than a and b.
In the same order, we can have many average and the process would stop. This leads to infinite number between a and b.
Notice that we talked about all the numbers moreover there are many irrational(non-terminating like 9.898989.... etc numbers as well.
Option (4), infinite solutions.
Note: we solved for all the number (not specifically odd, even, natural, whole, integer, etc).
