Riddle 1:
If it takes 5 machines, 5 minutes to make 5 tshirts; then how long will 100 machines take to make 100 tshirts?
Riddle 2:
There is a special offer at a garden shop. They sell super grass, a patch of which doubles in size everyday. Henry is very excited about this offer.
He figures out that if he buys 1 patch, it will cover his garden in 10 days. Henry decides to speed up the process, so he buys 2 patches of grass sod. How many days will it now take for the super grass to cover the whole garden?
Riddle 3:
A young man is travelling with his wolf and two sheep. The wolf likes the taste of sheep very much which means if the man leaves the sheep alone, the wolf will eat them. They come to a river and there is only one boat. Only the man and one animal can go on the boat at a time. So how do you think, they should cross the river?
Riddle 4:
Four criminals agree to play a game in order to gain their freedom. They are lined on some steps as shown in the picture below. They are all facing in the same direction. The door separates the 4th man.
Man 1 can see Man 2 & 3.
Man 2 can see Man 3.
Man 3 and Man 4 can see none of the others.
They know that they have been given 2 black hats and 2 white hats. But they initially don’t know the color of the hats they are wearing. They are told to shout out the color of their hats as soon as they are certain about the color they are wearing. They are not allowed to turn around; not allowed to talk to each other and not allowed to take off their hats either.
Who do you think will be the first person to shout out & why?
Riddle 5:
A good friend of yours challenges you and hands over a deck of 52 cards to you. He tells you 13 out of 52 cards are faceup, rest all the others are facedown and the faceup cards have been distributed randomly throughout the deck. You are blindfolded; you can’t see anything.. and you’re told to create a pile of cards with the same number of faceup cards & you have to use all the cards. So, how will you accomplish this seemingly impossible task. Remember you don’t know where the faceup cards are exactly in the deck.
Answers

 5 minutes. You can get easily fooled because of your intuition; but each machine takes 5 minutes to stitch 1 shirt.
 It will take only 9 days. If 1 patch covers the garden in 10 days, so it covers half of the garden in 9 days. Till 9 days each patch will take 9 days to cover half of the garden. So, 2 patches of super grass will take 9 days to cover the entire garden.
 He can take the wolf first and return with nothing. Then he can take one sheep and return with the wolf. Then take the second sheep and return with nothing and finally take back the wolf.
 Man 2 will be the first to shout out. That’s because Man 1 can see Man 2 & Man 3. If 2 and 3 have same colors then 1 will already be knowing the color of his hat. But if 2 & 3 are wearing different hat colors then based on 1’s silence 2 can shout out his own hat color – because 2 will know that if 2 and 3 are wearing different colors then in that case 1 will be confused about his own hat color.
 Take the first 13 cards and flip them over – this is the first pile. The second pile is the remaining 39 cards.
Let’s take an example – If in the 13 cards that you have taken out, there are 8 faceup cards; then after flipping there will be 5 faceup cards. While in the pile of 39, there were already 5 faceup cards (total faceup cards were 13 in total).
Therefore, faceup cards in pile 1 = faceup cards in pile 2 = 5, i.e. same number of faceup cards.