2,066 Medium Riddles With Answers - page 21 of 21
Can the mean of two consecutive primes be a prime?
The average of two numbers is the number exactly between them. All numbers between consecutive primes are composite by definition.
Can you swim faster in syrup or water?
The increased friction in syrup is balanced by the increased resistance the water provides for your stroke to push against. Studies (and Mythbusters) confirm this.
1) 1 penalty for �1k. 2) 2 of 3 for �1k. Choice?
If your skill (P) is > 0.5, the more trials you have, the more likely you are to succeed. If P < 0.5, take the single shot to maximize luck.
Place coins on round table. Last one wins. Go 1st or 2nd?
By going first and occupying the exact center, you can mirror any move the opponent makes on the opposite side of the table until they run out of space.
14ft pole. Up 5ft day, down 3ft night. Days to top?
The net gain is 2ft per 24-hr cycle. After 5 days, it is at 10ft. On the 6th day, it climbs 5ft to reach 15ft (crossing the 14ft mark) before the night slide.
How can the Earth's mass be measured?
By observing the gravitational pull (g) on the surface and knowing the Earth's radius, we can solve for M in the formula g = G * M / r^2.
Price reduced 23%. Increase needed to restore original?
If a $100 item drops to $77, you need to increase it by $23. $23 divided by $77 is approximately 0.2987, or 29.9%.
How many smartphones are there in London?
With a population around 9 million, and high smartphone penetration among adults and teens, 8 million is a logical estimate.
Ascend 9-7 Day 1, descend 9-7 Day 2. Spot reached at same time?
Intermediate Value Theorem: If you overlay the two trips on the same day, the climber going up and the one going down must meet at some point.
10R, 20B, 30G socks in 3 sizes. Min pull for matching pair?
There are 3 colors and 3 sizes = 9 unique combinations. In the worst case, you pull 9 different ones. The 10th must match one of the previous nine.
How many corners (vertices) does a tesseract have?
A point (0D) has 1 vertex. A line (1D) has 2. A square (2D) has 4. A cube (3D) has 8. Doubling each dimension, a tesseract (4D) has 16.
Choice: 1) Roll 1 die for $1M x result. 2) Roll 1M times for $1 x total.
The law of large numbers ensures Game Two will stay close to the expected value of $3.5M. Game One is high risk; you could end up with only $1M.
Brick thrown from boat into small pond. Does water level change?
When in the boat, the brick displaces its weight in water. When in the pond, it only displaces its volume. Since it is denser than water, its volume displacement is less than its weight displacement.
5 cats catch 5 mice in 5 mins. Cats needed for 100 mice in 100 mins?
If 5 cats take 5 minutes for 5 mice, then 1 cat takes 5 minutes for 1 mouse. In 100 minutes, that 1 cat can catch 20 mice. To catch 100, you need 5 cats.
How many gas stations are there in the United States?
This is a Fermi problem. Based on a population of 330 million and roughly 1 station per 2,000-2,500 people, 160,000 is a standard estimate.
9 marbles, one is heavier. Min weighings on a balance to find it?
Divide marbles into three groups of three. Weigh two groups. If they balance, the heavy marble is in the third group. Then repeat with the remaining three.
What is the sum of all the integers from 1 to 100?
Use the formula for the sum of an arithmetic series: n(n+1)/2. For n=100, it is 100*101/2 = 5,050.
With pointed fangs I sit and wait; physically joining with a single bite.
Describes the mechanical action of a stapler joining papers with metal fangs.
The person who makes it has no need; the buyer has no use; the user can't see/feel it.
The user is dead and cannot see or feel the casket they are in.
I never was, am always to be. No one ever saw me, nor ever will.
Tomorrow is always in the future; when it arrives, it is called 'today.'
Walks on four legs in the morning, two at noon and three in the evening.
Refers to the stages of life: crawling (4 legs), walking (2), and using a cane (3).
Greater than God, more evil than the devil... eat it and you'll die.
Poor people have nothing; rich people need nothing; and nothing is greater than God.
How can the number four be half of five?
The letters 'IV' are half of the four letters in the word 'FIVE.'
Forward I am heavy, but backward I am not.
'Ton' is a unit of heavy weight; spelled backward it is 'not.'
First 2 letters = male, first 3 = female, first 4 = great man, whole word = great woman.
The words are 'He', 'Her', 'Hero', and 'Heroine.'
You see a boat filled with people... you don't see a single person on the boat. Why?
A play on the word 'single' meaning unmarried versus 'single' meaning one person.
You measure my life in hours and I serve you by expiring. I'm quick when I'm thin and slow when I'm fat.
A thin candle burns through its length quickly, while a thicker one lasts longer.
I have lakes with no water, mountains with no stone and cities with no buildings.
A map represents these physical features symbolically on paper.
I am always hungry and will die if not fed, but whatever I touch will soon turn red.
Fire needs fuel to survive and leaves glowing red embers behind.
Nobody empties me, but I never stay full for long. What am I?
The moon cycles through phases, changing how full it looks.
I have no wings, but I can fly. And I have no eyes, but I can cry. What am I?
A cloud moves in the sky (flies) and produces rain (cries).
I have storms that rage for hundreds of years. My winds are the fastest. What am I?
The blue planet known for the Great Dark Spot and extremely high winds.
I'm not alive, but I can grow. I don't have lungs, but I need air. What am I?
Fire consumes oxygen (needs air) and spreads (grows).
A mother frog croaks "Ribbet-Ribbet." How does a baby frog croak?
A baby frog is a tadpole and hasn't developed a croak yet.
I am the fastest animal but cannot climb the tree. What am I?
The fastest land animal, but they don't climb well like leopards.
Who wears shoes while sleeping?
Horses wear iron shoes (horseshoes) even while sleeping.
The alphabet goes from A to Z but I go Z to A. What am I?
An animal whose name starts with Z, representing the end of the alphabet.
How do you catch a school of fish?
A pun on 'school' of fish and someone who loves books (a bookworm).
I bear the weight of knowledge on my shoulders every day. You'll find me full at dawn and lighter by the hallway. What am I?
Students carry their books in it; it gets lighter as books are used.
Imagine you are in a room with no windows or doors. How will you get out?
Since the situation is imaginary, the solution is too.
I make a loud sound when I'm changing. When I do change, I get bigger but weigh less. What am I?
Kernels pop loudly, expand in size, and become lighter.
How do you fix a damaged jack-o-lantern?
A pun on the location where pumpkins are grown.
Why were the little ghosts so successful in Little League?
A play on words involving the supernatural nature of ghosts.
How does a snowman lose weight?
When the temperature rises above freezing, the snow turns to water.
What kind of ball doesn't bounce?
A ball made from packed snow.
Which one of Santa's reindeer can be seen on Valentine's day?
Cupid is both the name of one of Santa's reindeer and the cherub associated with Valentine's Day.
I come in many colors, so beautiful and bright, I turn homes into a beautiful sight. What am I?
Electric decorations often used during the winter holidays.
I'm red all over, with dust in the air. Some people think I might have had water to share. What am I?
The fourth planet from the sun, known for its reddish hue.
I'm the planet with the most bling, I've got rings you can't help noticing! What am I?
The gas giant famous for its extensive ring system.
What has a spine but no bones?
A book's "spine" is the bound edge, unlike the bony spine of an animal.
I have a heart that doesn't beat?
A green vegetable whose center is called the heart.
I'm made of sand, and I might have a moat. Build me near water, but I'm not a boat. What am I?
A structure built of sand, often by children at the shore.
I am a word that begins with the letter "i". If you add the letter "a" to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?
An 'isle' is an island, while an 'aisle' is a passage between rows.
What word of five letters has one left when two are removed?
Remove the first two letters 'st' and you are left with the word 'one'.
I am a word of letters three; add two and fewer there will be. What word am I?
Adding 'er' to 'few' creates a word meaning a smaller number.
Forward I am heavy, but backward I am not. What am I?
If you read the word 'ton' from right to left, it spells 'not'.
What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?
The specific symmetry of these letters allows them to be read the same way.
Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?
Check the spelling of 'corner', 'room', and 'shelter'.
You see me once in June, twice in November and not at all in May. What am I?
Count the number of times the letter 'e' appears in each word.
A word I know, six letters it contains, remove one letter and 12 remains. What is it?
The word 'dozens' refers to multiple sets of 12.
What five-letter word becomes shorter when you add two letters to it?
Adding the suffix 'er' to the word makes it the word 'shorter'.
Two fathers and two sons are in a car, yet there are only three people in the car. How?
The three people represent three generations: child, parent, grandparent.
Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?
The doctors are female, making them Bill's sisters.
Mary has four daughters, and each of her daughters has a brother. How many children does Mary have?
The brother is shared by all the sisters.
What three numbers, none of which is zero, give the same result whether they're added or multiplied?
The sum and the product of these three specific integers are both 6.
I am an odd number. Take away a letter and I become even. What number am I?
Spell the word 'Seven' and remove the 's'.