i. If m and n are positive rational numbers, then m-n is positive.
The statement is not always true, for cases when the value of n is more than the value of m, then m-n is negative.
The statement is Sometimes True
ii. If m and n are negative rational numbers, then m +n is negative.
The addition of two negative numbers will always give a negative number.
The statement is Always True
iii. If m is a positive rational number and n is a negative rational number, then mn is negative.
The multiplication of a positive and a negative rational number will always give a negative number.
The statement is Always True
iv. If m and n are positive rational numbers, then mn is positive.
The product of two positive number will always give a positive number.
The statement is Always True
v. If mand n are negative rational numbers, then mxn is negative.
The product of two negative numbers is a positive number.
The statement is Never True