I am an odd number. Take away one letter, and I become even. What number am I?
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Seven
Take away the letter S from “seven” and you get “Even.”
Logic and Math Riddles: 24 Brain Teasers with Answers
Number patterns, word puzzles and tricky questions that need a little thinking. Every answer comes with the steps, so you can see how it works.
What comes next? 2, 4, 8, 16, …
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32
Each number is double the one before it, and double 16 is 32.
If you have three apples and you take away two, how many apples do you have?
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Two
You took two, so those two are the apples you have.
A doctor gives you three pills and tells you to take one every half hour. How long will the pills last?
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One hour
You take the first pill right away, the second after half an hour and the third after one hour.
Which is heavier: a pound of feathers or a pound of bricks?
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They weigh the same
Both weigh one pound. The bricks take up less room, but the weight is equal.
You are in a race and you pass the person in second place. What place are you in now?
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Second place
You took the second-place spot, and the person you passed is now third.
How many times can you subtract 5 from 25?
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Once
After the first time, you have 20, so you would be subtracting from a different number.
I’m thinking of a number. If you double it and add 6, you get 28. What is my number?
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11
Work backward: 28 minus 6 is 22, and half of 22 is 11. Check: double 11 is 22, and 22 plus 6 is 28.
What is the next letter? O, T, T, F, F, S, S, E, …
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N
The letters are the first letters of the numbers one, two, three and so on, so the next is “nine.”
A clock takes 5 seconds to strike six o’clock. How long does it take to strike twelve?
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11 seconds
There are five gaps between six strikes, so each gap is one second. Twelve strikes have eleven gaps.
Mary has four daughters, and each daughter has one brother. How many children does Mary have?
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Five
All four daughters share the same brother, so there are four girls and one boy.
Two fathers and two sons go fishing. They each catch one fish, but they bring home only three fish. How is that possible?
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There were only three people: a grandfather, his son and his grandson
The middle person is both a father and a son, so three people can be two fathers and two sons.
What do you get if you multiply all the numbers on a telephone keypad together?
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Zero
The keypad has a 0 on it, and anything times zero is zero.
What comes next? 1, 1, 2, 3, 5, 8, …
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13
Each number is the sum of the two before it, so 5 plus 8 is 13.
A farmer counts 20 heads and 56 legs in a barnyard with only chickens and cows. How many chickens and how many cows are there?
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12 chickens and 8 cows
12 chickens have 24 legs and 8 cows have 32 legs, which add up to 56.
Three light switches are in the hall. One of them turns on the lamp in a closed room, and you can open the door only once. How do you find the right switch?
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Turn the first one on for a while, then turn it off. Turn on the second, and go in
If the lamp is on, it is the second switch. If it is off but warm, it is the first. If it is off and cold, it is the third.
How many two-digit numbers have two digits that are the same?
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Nine
They are 11, 22, 33, 44, 55, 66, 77, 88 and 99.
A bat and a ball cost $1.10 together. The bat costs $1.00 more than the ball. How much does the ball cost?
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5 cents
If the ball is 5 cents, the bat is $1.05, and together they cost $1.10.
A snail is at the bottom of a 10-foot well. Each day it climbs up 3 feet, and each night it slips back 2 feet. On which day does it reach the top?
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Day 8
The snail gains one foot a day, but on the eighth day it climbs from 7 feet to 10 and does not slip back.
It takes 5 machines 5 minutes to make 5 toys. How long does it take 100 machines to make 100 toys?
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5 minutes
Each machine makes one toy in 5 minutes, so 100 machines make 100 toys in the same time.
A mom is four times as old as her son. In 20 years, she will be twice his age. How old is the son now?
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10 years old
Now the mom is 40. In 20 years, she is 60 and her son is 30, which is half.
I am a three-digit number. My tens digit is 5 more than my ones digit, and my hundreds digit is 8 less than my tens digit. What number am I?
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194
The tens digit must be 9 so that the hundreds digit is 1, and then the ones digit is 4.
A ladder hangs over the side of a ship, and 8 of its rungs are under the water. The tide rises 4 feet in two hours. How many rungs are under water then?
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Still 8
The ship floats, so it rises with the water and the ladder stays at the same level.
Add together eight 8s to make 1,000, using only addition signs.
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888 + 88 + 8 + 8 + 8 = 1,000
888 plus 88 is 976, and the three 8s add 24 to make 1,000.