Hey Greg,

Can you please share your strategy to solve this question? I got it right but took me time to solve.

Hey Greg,

Can you please share your strategy to solve this question? I got it right but took me time to solve.

For this type of questions, I like choosing numbers and also eliminating answer choices that I can contradict. The most important thing is to keep in mind the initial conditions that you are given, in this case, 0<st<1.

First, notice that answer choice E makes completely no sense, so we can discard that answer choice. If you are skeptical, choose s=2 and t=2 so st=4 so we violate our given conditions.

Notice that answer choice B is kind of similar, choose s=-2 and t=-3 so st=6 which is not what we want. We discard this answer choice. Now we are left with A, C or D

Notice that A deals with s being negative and t being positive, so the product st would be negative. Again, this doesn’t work for us. Discard it.

Notice that D is kind of similar to A, because we are dealing with s positive and t negative, so st would be negative.

Thus, answer choice C must be the correct one. Can you come up with an example?

Try to prove each statement wrong

s=(-1/2)

t=(-3/2)

st = 3/4

0<3/4<1

Thanks