take a guess
To make a prediction, estimate, or conjecture; to guess. If I had to take a guess, I'd say that it's the cooling system that failed. You won't be penalized for taking a guess, so be sure not to leave any questions unanswered.
take a guess
and hazard a guess; make a guessto guess. Even if you don't know, please take a guess. If you don't know the answer, hazard a guess.