Logic & Riddles

All Logic & Riddles questions (100)

• A bat and ball cost $1.10. The bat costs $1 more than the ball. What does the ball cost?
• If 5 machines take 5 minutes to make 5 widgets, how long for 100 machines to make 100 widgets?
• A lily pad doubles in size every day. It covers the lake in 48 days. When was it half covered?
• You have two ropes that each take 1 hour to burn (unevenly). How do you measure 45 minutes?
• A farmer has 17 sheep. All but 9 die. How many are left?
• Two fathers and two sons go fishing. They catch 3 fish, one each. How?
• A man runs a mile south, mile east, mile north, ends where he started. Where is he?
• You drive 60 km at 30 km/h. How fast to average 60 km/h for 120 km total?
• I have cities but no houses, forests but no trees, water but no fish. What am I?
• A plane crashes exactly on the US-Canada border. Where do they bury the survivors?
• 3 people check into a hotel room for $30 ($10 each). Manager returns $5. Bellboy keeps $2, returns $3. Each paid $9 (total $27) + $2 = $29. Where's the missing $1?
• How many times can you subtract 5 from 25?
• A ship takes 6 days to sail from port A to B. If it leaves on Friday, which day does it arrive?
• You're in a race and pass the person in 2nd place. What place are you now?
• A doctor gives you 3 pills and says take one every 30 minutes. How long do they last?
• If you have a 3-gallon and 5-gallon jug, how do you measure exactly 4 gallons?
• A snail climbs 3 feet per day but slips 2 feet at night. How many days to climb 10 feet?
• You see a boat full of people but not a single person is on it. How?
• What weighs more: a pound of feathers or a pound of bricks?
• If it takes 8 men 10 days to build a wall, how long for 4 men?
• A monkey climbs 30 ft pole. Each hour climbs 3 ft and slips 2 ft. Time to reach top?
• Three switches control three bulbs in another room. You can enter the room only once. How to identify all three?
• Two coins total 30 cents. One is not a nickel. What are they?
• An electric train moves north at 100 mph. Wind blows east at 40 mph. Which way does smoke blow?
• You have 12 identical coins. One is fake (lighter or heavier). Minimum weighings on a balance to find it?
• A is B's brother. B is C's father. What is A to C?
• What can run but never walks, has a mouth but never talks?
• How can you drop a raw egg from a height without breaking it?
• A windowless room has 3 light bulbs inside. Outside are 3 switches. You may enter only once. How many bulbs can you definitely identify?
• What gets wetter the more it dries?
• You walk into a dark room with a match. There's a candle, a fireplace, and a gas lamp. What do you light first?
• A man builds a house with all 4 sides facing south. A bear walks by. What color is it?
• Forward I am heavy, backward I am not. What am I?
• If you had only one match and entered a dark room with an oil lamp, newspaper, and kindling, what would you light first?
• Is it legal for a man to marry his widow's sister?
• How many birthdays does the average person have?
• A truck driver goes the wrong way down a one-way street. A cop sees but doesn't stop him. Why?
• What occurs once in a minute, twice in a moment, but never in a thousand years?
• How far can a dog run into a forest?
• What has keys but no locks, space but no room, and you can enter but can't go inside?
• Turn me on my side and I am everything. Cut me in half and I am nothing. What am I?
• A boy and his father crash. Father dies. At hospital, surgeon says 'I can't operate, he's my son.' Who is the surgeon?
• You are a cyclist in a race. You pass the last person. What's your position?
• I speak without a mouth and hear without ears. I have no body but come alive with wind. What am I?
• What disappears as soon as you say its name?
• A girl fell off a 50-foot ladder but didn't get hurt. How?
• What has a head and tail but no body?
• What can travel around the world while staying in a corner?
• If there are 3 apples and you take 2, how many do you have?
• The more you take, the more you leave behind. What am I?
• In the Monty Hall problem, you pick door 1. Host opens door 3 (goat). Should you switch to door 2?
• How many people needed in a room for >50% chance two share a birthday?
• Multiply all digits on a phone keypad (0-9). What's the product?
• A clock strikes 6 in 5 seconds. How long to strike 12?
• You flip a fair coin 5 times and get heads each time. What's the next flip most likely?
• If you have 9 coins and one is heavier, minimum weighings on a balance to find it?
• A train leaves station A at 60 mph. Another leaves B at 40 mph toward A. Stations are 100 miles apart. Where do they meet?
• You meet two guards. One always lies, one always tells truth. One door leads to freedom. One question to ask one guard to find the safe door?
• What is 1/2 of 2/3 of 3/4 of 4/5 of 100?
• A father is 4 times his son's age. In 20 years, he'll be twice his son's age. How old is the son now?
• If you fold a paper in half 50 times, approximately how thick would it be?
• 10 people meet and each shakes hands with everyone else. How many handshakes?
• You need to make exactly 100 fence posts for 100 meters with a post every meter. How many posts for a straight line?
• If two's company and three's a crowd, what are four and five?
• A fox, chicken, and grain need to cross a river. Boat fits farmer + 1 item. What goes first?
• What are the chances of rolling at least one six in four rolls of a die?
• If pipe A fills a tank in 6 hours and pipe B in 4 hours, how long together?
• In Zeno's paradox, Achilles gives a tortoise a head start. Can he overtake it?
• What is the next number: 1, 11, 21, 1211, 111221, ?
• If all Bloops are Razzies, and all Razzies are Lazzies, are all Bloops definitely Lazzies?
• Two ducks in front of a duck, two ducks behind a duck, one duck in the middle. Minimum ducks?
• You draw 2 cards from a 52-card deck. Probability both are aces?
• A square room has a clock on each wall. How many clocks show the same time?
• A ladder leans against a wall. Bottom slides out. What shape does the middle trace?
• You have 2 hourglasses: 7-min and 11-min. How to time exactly 15 minutes?
• If December 31 falls on Thursday, what day is January 1?
• You have 8 balls. One is heavier. You have a balance scale. Minimum weighings to find it?
• I am an odd number. Remove one letter and I become even. What am I?
• A woman has 7 daughters and each has a brother. How many children total?
• What probability of getting exactly 2 heads in 3 fair coin flips?
• A man is twice as old as his daughter. 20 years ago he was 6 times her age. How old is the daughter?
• You cut a pizza with 3 straight cuts. Maximum number of pieces?
• A king wants to test 1000 wine bottles for poison using prisoners. Poison kills in 24hrs. Minimum prisoners needed?
• If you rearrange 'CIFAIPC', you get the name of a(n)?
• A rope is tied around the Earth's equator. Add 1 meter of rope. How high off the ground can it rise uniformly?
• Three people each flip a coin. What's the probability all three match?
• If you write all numbers from 1 to 100, how many times do you write digit 9?
• 3 missionaries and 3 cannibals cross a river. Boat holds 2. Cannibals must never outnumber missionaries on either bank. Minimum crossings?
• What is the angle between clock hands at 3:15?
• You roll two dice. What's the probability the sum is 7?
• If A can do a job in 10 days, B in 15 days. They work together for 4 days, then A leaves. How many more days for B alone?
• A triangle has sides 3, 4, and 5. What type of triangle is it?
• You have 3 boxes: one has 2 gold, one has 2 silver, one has 1 of each. Labels are ALL wrong. Pick one coin from one box. Can you label all boxes?
• An island has people who say 'yes' or 'no'. You ask someone 'Are you a truth-teller?' What do both types answer?
• What is 0.999... (repeating) equal to?
• A bucket weighs 5 kg when full of water. It weighs 3 kg when half full. What does the empty bucket weigh?
• Divide 30 by 1/2 and add 10. What do you get?
• Three envelopes: one has $100. You pick one, then 1000 empty ones are removed from the remaining. Switch?
• A worm is at the bottom of a 12-cm rubber band. Band stretches 12cm each second. Worm crawls 1cm/sec. Does it reach the top?
• You have a 5-minute and 3-minute hourglass. How do you time exactly 1 minute?