I + f - f' is an even integer, where I is an integer, f and f' are proper positive
fractions (0 < f, f' < 1). Then the integer I is an odd number.
False
let us consider f - f' separately,
0 < f < 1 and 0 < f' < 1
f - f' will attain its maximum value when f = 1 and f' = 0 and it will attain its
minimum value when f = 0 and f' = 1.
⇒ -1 < f - f' < 1
I + f - f' is an even integer.
I is also an integer. For I + f - f' to be an integer, f - f' should also be an integer.
The only integer value it can take is 0, because -1 < f - f' < 1.
⇒ f - f' = 0
⇒ f = f'
⇒ I + f - f' = I = an even integer