It’s 47

I would go to the barber with the messy hair, because his hair shows that he has so much work that he has no time to trim his hair nicely.

It is obvious that the possible days are WEDNESDAY or FRIDAY, but since A Says D and I wanted to go earlier in the week but there wasn’t day when we could both take care of our errands,
it can’t be Friday because this statement will be false, so only Wednesday is left!!

It can be solve mathematically as Srihari Bharatthi did, but we can solve it by using common sense. We know that if he turns back he passes a quarter of the way and he’ll meet the train, so if he runs the opposite direction after a quarter of the way the train is now an the beginning of the tunnel.  So at this point he has to run half of the tunnel and the train travels the whole tunnel at the same time, which means that the train speed is twice his speed, so its 40mph

The three sets of lyrics for children that all share a common melody are the ABC Song, Twinkle Twinkle Little Star, and Baa Baa Black Sheep. These are all variations of a 1761 French melody called Ah vous dirais-je, Maman by Bouin.

Many people think Mozart composed this melody. In fact, he wrote twelve variations of Bouin’s work which brought it to a larger audience.

8:32

If Jacob got the hour 6, he could not say that Tony does not know the answer because he might got 6:43. The same applies to 7 because Tony could have 7:46. So that leaves us that Jacob got the hours 8 or 9. The possible minutes are 17,19,32,50 and for each of them Tony has more than one possibility so Jacob can say for sure that Tony does not know the answer.

Now, if Jacob got 9 and Tony 50 or 17, Tony will say he knows the answer, but Jacob wouldn’t know (because there is more than one possibility this hour). And if Tony got 19 he still does not know, therefor since he said he knows the answer  can not be 8:19 and that leaves us with 8:32

The difference between the numbers is 4,4,-7 etc’ so the missing number is 20.

I found a simpler answer than the one i gave above. Jacob will ask:
If you subtract 2 from your number,  will the result be positive?
No means the chosen number is 1.
I don’t know the chosen number is  2 (since zero in neither positive nor negative)
Yes means the chosen number is 3.

Jacob will  ask: If I’ll draw a function of the degree of the number you have chosen will it have extremum?
A 1st degree function is a straight line so the answer is no.
A 2nd degree function has an extremum point so the answer is yes.
A 3rd degree function might  have an extremum point but not always’ so the answer will be “I don’t know”