Logic Teasers

Question 1
3 girls go to the shop for a gift for a friend. Each puts in $ 10 towards the gift. They choose a gift that is worth $25. Instead of returning $5, the dishonest cashier returns $3 and pockets $2. Each girl takes back $1 from the returned $3.So effectively they paid $9 towards the gift. Total the girls paid is $9 thrice which is $27. The cashier took away $2. Which makes it a total of $29. Where did $1 from the $30 disappear?
Answer
Though initially each girl put in $10 for the gift, $25 has been paid towards the gift. Of the $5 to be returned to the girls, $2 is taken by the cashier and $1 each returned to the girls making it a total of $30.
The payment should equal the receipts and the logic in adding money in the above is flawed. 
Question 2
What is special about the following sequence of numbers?
8 5 4 9 1 7 6 10 3 2 0Answer
The numbers are in alphabetical order.
(eight, five, four, nine, one, seven, six, ten, three, two, zero) 
Question 3
A pen and its gift box together costs $110. The Pen costs $100 more than the gift box. How much does the gift box cost?
Answer
$5

Question 4
R / E / A / D / I / N / G  What is this?
Answer
Reading between the lines

Question 5
If you took 6 apples from a basket with 10, how many would you have?
Answer
6 as you took 6

Question 6
Five ladies Sarah, Brenda, Mary, Annie and Kate are seated in 5 chairs lined against the wall. The chairs are numbered one to five, the first one being near the door. From the given clues can you find on which of these chairs each lady is sitting?
 Sarah has a lady sitting on both her sides.
 Annie has the same number of ladies on both her sides.
 Kate has no one sitting on one side.
 Brenda sits between Mary and Annie.
 Mary does not sit near the door.
Answer
Kate sits on the first chair near the door.
Sarah, Annie, Brenda and Mary on second, third, fourth and fifth chair respectively. 
Question 7
 If you remove the first letter, a bit remains.
 If you remove the second, bit still remains.
 After much trying you might be able to remove the third one also, but it remains. What is it?
Answer
Habit
Remove H: "a bit" remains
Remove A: "bit" remains
Remove B: "it" remains

Question 8
A rooster lays an egg at the very top of a slanted roof. Which side is the egg going roll on?
Answer
Roosters don't lay eggs

Question 9
My next door neighbour lies a lot. In fact, he only tells the truth on one day a week! One day he told me, "I lie on Mondays and on Tuesdays."
The next day he said, "Today is either Thursday, Saturday or Sunday."
The next day he said, "I lie on Wednesdays and Fridays."
On which day of the week does my neighbour tell the truth?Answer
My neighbour tells the truth on Tuesdays. Take them one at a time and assume he is telling the truth on each of the three days that he makes a statement. Then assume he is not telling the truth on any of the days that he makes a statement. The only case that works is the one where he is telling the truth on the third day. On that third day, from the statements he made, he lies on Wednesdays and Fridays. He tells the truth on Mondays and Tuesdays. Yesterday was not Thursday, Saturday or Sunday. That means that he couldn't be telling the truth on Monday because yesterday can't be Sunday and therefore, he must tell the truth on Tuesdays.

Question 10
The number of marbles in a box doubles every minute. The box is full in 26 minutes. When was the box half full?
Answer
25 minutes

Question 11
While exploring the amazon, wild man Peter was captured by hostile wood fairies. Keith, the powerful chief of fairies told him, he could make one final statement which would determine how he would die.
 If the statement he made was fault, he would be boiled in water.
 If his statement was true, he would be fried in oil.
Wild man Peter found neither of these options to his liking, So he made a statement that got him out of this impossible situation. What is the statement that he would have made?
Answer
Wild man Peter said "You will boil me in water".
The fairies were faced with dilemma. If they boiled him in water, that would make his statement true. Which means he should have been fried in oil. They can only fry him in oil if he makes a true statement But if they do, it would make his final statement false.
The fairies had no way out of their situation and so were forced to set wild man Peter  Free 
Question 12
Two fathers and two sons went fishing. Each caught a fish. But only three fish were caught. How come?
Answer
There were only three people, a son, father and grandfather.

Question 13
There are 10 black socks and 10 white socks in a drawer. What is the maximum number of socks should you should draw out one at a time without looking to make sure you have a pair of the same colour?
Answer
Three

Question 14
What number should replace the question mark?
3 6 9 18 27 54 ?
Answer
81. Multiply with 2 and 1.5 alternatively

Question 15
You have a three gallon and a five gallon measuring device. You wish to measure out four gallons  How?
Answer
Fill the five gallon container. Pour all but two gallons into the three gallon container. Empty the three gallon container. Put the two remaining gallons from the five gallon container into the three gallon container. Fill the five gallon container one more time. Pour one gallon from the five gallon container by filling the three gallon container. Now the five gallon container contains four gallons.

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