Yes, absolutely, if you can come up with an example that satisfies all of the conditions in the question, then that can be used to identify the correct answer in case of a problem solving question. Of course it is not easy to come up with an example in all cases because this method relies on trial and error, but yes this approach will work.

Also, keep in mind that a there may be cases where resorting to examples may not work or could be exceedingly difficult.

Here is an example of a problem that might be difficult to do by trial and error using the answer choices. This might even be too difficult for the GMAT, but if you can handle a problem like this then you are close to the Q51 target.

I have done it differently, but I am not sure if this way would be consistent with other questions.
so I considered my integer to be “ab” and so the difference with the reverse would be ba-ab = 27

or

ba –
ab =
27

my assumption here is that “a” is smaller than “b”, that’s why I doubt this method would be applicable with other questions.

You are trying to do the subtraction with the digits, how we typically do with numbers, and it can certainly work but it is harder to deal with. I would just stick with place value set up. In this case you don’t have to worry about carry over and all those other constraints.

Saransh Saxena says

Can’t we solve it like this

96-69=27 and the difference between the digits will be 9-6=3.

GMAT Quantum says

Yes, absolutely, if you can come up with an example that satisfies all of the conditions in the question, then that can be used to identify the correct answer in case of a problem solving question. Of course it is not easy to come up with an example in all cases because this method relies on trial and error, but yes this approach will work.

Also, keep in mind that a there may be cases where resorting to examples may not work or could be exceedingly difficult.

GMAT Quantum says

Here is an example of a problem that might be difficult to do by trial and error using the answer choices. This might even be too difficult for the GMAT, but if you can handle a problem like this then you are close to the Q51 target.

Yousef says

I have done it differently, but I am not sure if this way would be consistent with other questions.

so I considered my integer to be “ab” and so the difference with the reverse would be ba-ab = 27

or

ba –

ab =

27

my assumption here is that “a” is smaller than “b”, that’s why I doubt this method would be applicable with other questions.

this gives that 10+a – b = 7 and so b-a=3

and b-1 – a = 2 which gives that b-a =3

GMAT Quantum says

You are trying to do the subtraction with the digits, how we typically do with numbers, and it can certainly work but it is harder to deal with. I would just stick with place value set up. In this case you don’t have to worry about carry over and all those other constraints.