Difficulty Popularity

You have ten sets of 10 coins. You are aware of exactly how much the coins weigh. You also know that all the coins in one set of ten are exactly a hundredth of an ounce off which makes the entire set of the ten coins a tenth of an ounce off. Also you are aware of the fact that all the other coins weight the correct amount. Now you are allowed to use an exceptionally precise digital weighing machine only once.

Can you identify which set of 10 coins is faulty?

Can you identify which set of 10 coins is faulty?

Difficulty Popularity

Three best logicians are brought into a room. Each of them has been painted a number on their forehead with a number that is unique and greater than zero. You are one of them and can see other two foreheads with the number 20 and 30 painted on them. The game begins and the host circles around the logicians asking each one of them to guess the number written on their forehead. Each of the logician is unable to answer and says that he can't guess it. Then the question is asked again.

What is your number and why?

What is your number and why?

Difficulty Popularity

The scenario comprises of a wobbly bridge and four people. It is the night time and the people have only one torch. Without torch one may risk his life in crossing the bridge. Also we have a condition; the bridge is not quite strong and can hold only two persons together at one. The four people take different time to cross the bridge - 1 min, 2 min, 7 min and 10 min.

Since the torch is a necessity and the bride can't hold more than two persons at a time, two persons must travel at a time out of which one must return with the torch so they don't risk their life crossing in the dark.

What is the shortest time that will be required for all of them to cross the bridge?

Since the torch is a necessity and the bride can't hold more than two persons at a time, two persons must travel at a time out of which one must return with the torch so they don't risk their life crossing in the dark.

What is the shortest time that will be required for all of them to cross the bridge?

Difficulty Popularity

Nine brilliant most students were summoned by an inspecting professor. He gave them a situation and told them that he is having nine hats. The hats are either red colored or blue colored as told by the professor. He also tells them that he have at least one red colored hat and the number of blue hats are greater than the red hats.

He places one hat on each of their heads. The students are not allowed to talk with each other and no means of communication is feasible. He asks them how many hats are blue and how many are red. He gives them half an hour to deduce and moves out of the room. Nobody is able to answer when he returns back and thus he gives them another fifteen minutes. But when he returns, no one can answer again. Thus he gives them final five minutes. On returning back this time, everyone was available with an accurate answer.

How could the students have deduced the right answer? What is the right answer?

He places one hat on each of their heads. The students are not allowed to talk with each other and no means of communication is feasible. He asks them how many hats are blue and how many are red. He gives them half an hour to deduce and moves out of the room. Nobody is able to answer when he returns back and thus he gives them another fifteen minutes. But when he returns, no one can answer again. Thus he gives them final five minutes. On returning back this time, everyone was available with an accurate answer.

How could the students have deduced the right answer? What is the right answer?

Difficulty Popularity

There is a ground where the grass grows up with a uniform rate in length and thickness. If forty cows can eat whole of the grass in forty days and thirty cows can eat the whole grass in sixty days.

How much time will twenty guys take to eat whole of the grass ?

How much time will twenty guys take to eat whole of the grass ?

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Wha...

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