The number of natural numbers between 15 and 20 is ___.
There are only 4 natural numbers between 15 and 20 which are 16, 17, 18 and 19.
The number of natural numbers between 15 to 20 is/are ___.
The sum of two natural numbers is 15 and the difference between their squares is 15. The difference between the numbers is ___.
How many natural numbers lie between 9 and 15?