Sentence Correction

On Princeton Review, it mentioned that:
- always use "whether" when it means two possible conditions/outcomes, such as
"I don't know whether my proposal will be approved."

- always use "if" when it means a precondition, such as
"If he becomes a member of the club, I'll quit."

I don't see similar instruction on OG though. Can someone confirm the useage of these 2 words? I have no question on using "if" with conditional clause, but I'm not sure I can only use "whether" for two possible conditions...

Hi pakaskwa..

I would like to clear your doubt based on my knowledge.

"IF" is always used when it is followed by a "THEN", i.e. "IF" is used in case of a conditional sentence
For eg (d one u used) - If he becomes a member of the club, (THEN) i will quit.

And "Whether" is used when the sentence does not intends to be conditional.
For eg - "I dont know WHETHER my proposal will be approved".

If u look at both d egs den u must notice dat in d first eg the person specifies dat wat is he gonno do if sum1 becomes d member of d club, which is introduced by the then clause.
However in the second eg the person is only doubtful dat whether his proposal will be approved or not. He does not speaks of the aftermaths of the event (approval or rejection) dat is goono take place.

Hope i cleared ur doubt. If u still hv questions plz post it.