Weekly Puzzle

1Two large flat mirrors are kept standing on the floor, at an angle of 60 degrees to each other. If I stand in between them holding a lightbulb, then how many lightbulbs in all can I see (including the one I am holding)?Solve this puzzle
236 coins are arranged in a 6x6 square grid fashion. What are the maximum number of coins that you can remove, if you have to ensure that every row and column has at least 2 coins remaining?Solve this puzzle
3There is a 100-liter water tank; whose input pump can be used to fill it at the rate of 1 liter every 2 minutes; and the outlet valve can consume 1 liter every 5 minutes.
The tank contained 80 liters when the outlet valve was opened at 10:00 AM. If the tank now contains 50 liters of water at 3:00 PM, then for how many minutes has the input pump remained active?
Solve this puzzle
4A king has been trapped alone in a castle. There is one switch in each of the 4 corner towers; and only when each of them is set to a correct (ON/OFF) position, will the main gate open. Every time the king runs from the central hall to any one corner tower, changes the switch, and returns to check the gate, it takes him 1 minute.
What is the least amount of time in minutes, in which the king can be guaranteed to escape from the castle? (You may assume that all switches start in the OFF position)
Solve this puzzle
5There was a 100-acre beach plot in the year 2010, but each year about 2 acres of the land gets permanently submerged due to the rising sea level. The plot is to be exactly divided between 3 brothers; with the legal clause that each brother will get as many acres as his own age. If the brothers were born in the years 1986, 1988 and 1991, then in which year will they be able to divide the land between themselves? Solve this puzzle
6Three teachers and three students are standing on the shore of island A, along with a three-passenger boat. The students want to reach island B, and the teachers want to reach island C. If each of the islands A, B and C is exactly 1 kilometer away from the others, then what is the minimum distance in kilometers that the boat would travel, in order for everyone to reach their destination?Solve this puzzle
7Players 1, 2 and 3 are playing a game on an 8x8 chessboard. In each turn, the player places a rook on any vacant square; provided that it is not being attacked by the rooks already placed before. The player who has no move left, wins the game. If player #1 plays first, followed by #2 and #3 in that order, then which player will win the game? (Give your answer as 1, 2 or 3)Solve this puzzle
8In the list of "top 50 songs", artists A and B have contributed to 25 songs and 35 songs each. If both A and B have collaborated on more than 7 songs, then what is the maximum number of songs on which B has worked alone?Solve this puzzle
9A square plot of land contains 150 trees . The owner wants to divide the land using fences, such that each section contains at most 12 trees. If all the fences are straight line segments of any length, then what is the least number of fences that are guaranteed to be required?Solve this puzzle
10On 31 Dec 1898, a person would write his own calendar for the year 1900. He begins to write only the day numbers first, but runs out of ink after writing exactly 600 digits. What is the last day that was written?
Answer in the dd-mm format; eg. 24-03
Solve this puzzle
11What is the next number in this series?
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12If 1st Jan 2000 was a Saturday; what day will 1st Jan 2100 be?Solve this puzzle
13A 300-meter long train is travelling at the speed of 100 km per hour. One engineer keeps walking back and forth between the front compartment and the rear one, at the speed of 2 km per hour.
If the train's journey is 300 km long, then how many meters has the engineer walked in the same time?
Solve this puzzle
14During the rainy season, a playground of size 50 meters by 100 meters has to be covered with square carpets of size 20x20 meters. If none of the carpets can be folded or overlap other carpets, but some carpets can go outside the borders of the ground, then how many carpets will be needed?Solve this puzzle
15A digital clock contains some fault; due to which two of the straight segments used in the display digits, remain permanently off. At one point, the clock showed the time "06:45". Almost 1 hour later, it showed the time "05:39". Exactly how many minutes elapsed between the two readings?Solve this puzzle
16A travelling agency wants to provide bus services between 10 cities. Each city may not have a direct bus route to reach every other city, but the agency wants to ensure that any city can be reached from any other using atmost 2 connecting bus routes. What is the minimum number of routes that the agency needs to offer, for satisfying this condition?Solve this puzzle
17The town hall contains 3 bells: the first one rings once every 6 minutes, the second rings once every 15 minutes, and the third one rings once every 21 minutes. If the bells rang together for the first time at midnight, then what is the shortest time interval (in minutes) during the rest of the day, for which no bells were ringing?Solve this puzzle
18A growing kitten consumes more milk with each day; to be precise it increases its daily milk consumption by a fixed amount every day. On the first day it consumed 100 ml of milk; and by the end of day 6, it had consumed a total of 900 ml. How much total milk in milliliters, will it have consumed by the end of day 12?Solve this puzzle
19What is the maximum number of bishops that can be placed on a standard 8x8 chessboard, such that no two bishops are attacking each other? (In chess, a bishop can attack along only the diagonal direction.)Solve this puzzle
20A cylindrical tower is 14 meters in diameter, and 33 meters in height. Along its outer wall, there is a staircase that spirals around the tower. It goes from the ground floor to the topmost one, and completes one full revolution around the tower. What is the total length of the staircase, in meters? (You may approximate PI to 22/7)Solve this puzzle
21Five players named A,B,C,D,E are playing a game with a bar of chocolate squares, starting with a single rectangular piece of size 6x8. They take turns in the order A to E, starting with player A. In each turn, a player takes any one existing piece, and splits it into two smaller pieces along one of the ridges. The game ends when the chocolate has been completely divided into individual single squares. Who makes the last move of the game?Solve this puzzle
22A shopkeeper wants to buy several weight stones for his pan balance; using which he would be to able to measure all multiples of 1 kg, starting from 1 kg upto 10 kg. There are stones of every weight available for him to purchase. What is the minimum number of stones that the shopkeeper will have to buy? Solve this puzzle
23There are eight identical-looking coins. Six of them are genuine ones weighing 10 grams each; but the remaining two are fake and weigh 12 grams each. Using just a pan balance, what is the minimum number of trials needed to determine both the fake coins?Solve this puzzle
24A boat has got lost in a river due to dense fog. The captain does know that the river is uniformly 7 kilometers wide; and flows in a straight line i.e. without any bends or turns. What is the minimum distance in kilometers in which the boat can be guaranteed to reach a river bank?Solve this puzzle
25In an archery contest, the judge decides some target score X, where X can be any number from 1 to 30. Then the participant fires multiple arrows at a target, one after the other; till he precisely achieves a total score of X. For each arrow, hitting the center "bull's eye" of the target is worth 10 points; and the surrounding rings are worth 6, 3 and 1 points respectively. (The participant is allowed to hit the same region more than once). What is the minimum number of arrows that will surely be enough, regardless of what X is?Solve this puzzle