GreenlightTestPrep wrote:
If p and q are positive integers, and p < q, then which of the following MUST be true?
I) p/q < (p+1)/(q+1)
II) (p–1)/q < (p+1)/q
III) (p–1)/q < (p–1)/(p+1)
A) I only
B) I and II only
C) I and III only
D) II and III only
E) I, II and III
Statement I: There's a nice rule that says "If we add the same positive value to the numerator and denominator of a positive fraction, the resulting fraction is closer to one than the original fraction was.
For example (23+8)/(50+8) is closer to 1 than is 23/50
Since p < q, we know that p/q is less than 1
By the above rule, we know that (p+1)/(q+1) is closer to 1 than is p/q, which means p/q < (p+1)/(q+1) < 1
Statement I is TRUE
Statement II: The positive denominators are the same, but the numerator p+1 is greater than p-1
So, it must be the case that (p-1)/q < (p+1)/q
Statement II is TRUE
Statement III: This time the numerators are the same, but the denominators are different (q and p+1)
We can right away that if p = 1, then the two sides are EQUAL
In other words, it is NOT the case that (p–1)/q < (p–1)/(p+1)
Statement III need NOT be true
Answer: