Seriously there is no definitely answer as it differs for every guy
For me, i will agree if i am interested in the girl, if not i will tell her straight. Going out with her would only make her get the wrong idea, and eventually hurt her more
On the other hand, i also has some friends who would go due to obligations and not to disappoint the girl. Well seems like they find saying NO to a girl quite difficult.
But for your case, since he has already agreed to going out with you, prolly that means he is willing to give you and him a chance to get to get to know each other better. Well you can also check his attitude to you whn he goes out with you. If his attitude is cool, well then you should get the hint. If he is damn passionate and keep chatting with you, the feeling is mutual.
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