Four Weights To Thirty

What four weights can be used to balance from one to thirty pounds?

A = 1
B = 3
C = 9
D = 17

1 lb = A
2 lbs + A = B
3 lbs = B
4 lbs = A + B
5 lbs + A + B = C
6 lbs + B = C
7 lbs + B = A + C
8 lbs + A = C
9 lbs = C
10 lbs = A + C
11 lbs + A = B + C
12 lbs = B + C
13 lbs = A + B + C
14 lbs + B = D
15 lbs + B = A + D
16 lbs + A = D
17 lbs = D
18 lbs = A + D
19 lbs + A = B + D
20 lbs = B + D
21 lbs = A + B + D
22 lbs + A + B = C + D
23 lbs + B = C + D
24 lbs + B = A + C + D
25 lbs + A = C + D
26 lbs = C + D
27 lbs = A + C + D
28 lbs + A = B + C + D
29 lbs = B + C + D
30 lbs = A + B + C + D

Posted in Brain Teasers

What is the Five Digit Number?

What 5-digit number satisfies the following requirements?

1. No zeroes
2. First two digits are the same
3. Fourth digit is twice the first
4. Last digit is twice the third
5. Sum of all digits is 18

33264.

There are several ways of solving this. One way is to represent each spot with a letter, A – E.

Then you have these equations:

A = B
D = 2 * A
E = 2 * C
A + B + C + D + E = 18

By simplifying, you get:

4 * A + 3 * C = 18

Plug in values for A and C to find that A = 3 C = 2.

Posted in Brain Teasers

Fewest Queens For Full Attack

What is the smallest number of queens required on a chess board to attack all squares?

5. To see where they need to be placed, check out the diagram on Wolfram’s Queens Problem page.

Posted in Brain Teasers

Take It And You Will Lose

Take it and you will lose or gain more than all others.

Risk.

(found in The Copper Gauntlet by Holly Black and Cassandra Clare)

Posted in Riddles

Name That Song

James makes a bet with Laura that he can use any name she can think of in a song she will recognize with the original lyrics. Laura takes him up on the bet and loses. What song did James sing to win?

Happy Birthday. When you sing Happy Birthday, you say the person’s name as part of the song.

Posted in Brain Teasers

I Start Out The Same As Others

I start out the same as others,
Then grow to four legs and four arms,
And two hearts beat inside,
Until the separation.

What am I?

A pregnant woman is like other women, then the baby forms, and then is delivered.

Posted in Riddles
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The Longest Pregnancy

A baby was born four years after its parents died in a car crash. How was this possible?

Amazingly, this actually happened. The parents died in a crash crash and their parents fought for the rights to the four frozen embryos left by their late children. After a surrogate pregnancy, the baby was born with DNA matching their deceased parents.

Posted in Brain Teasers

A Red Robe and Staff In Hand

I wear a red robe,
With staff in hand,
And a stone in my throat.
Cut me and I weep red tears

What am I?

A cherry

There are a few other variations of this one:

As I went through the garden gap,
Who should I meet but Dick Red-cap!
A stick in his hand, a stone in his throat,
If you’ll tell me this riddle, I’ll give you a groat.
(Said to be the lyrics to A Cherry)

I slipped down a slippery gap,
Found a man with a red cap,
He had a stick in his back and a stone in his belly,
Riddle me this and I’ll give you a penny.

Posted in Riddles

I’m On A Horse

You’re riding a horse. To the right of you is a cliff and in front of you is an elephant moving at the same pace and you can’t overtake it. To the left of you is a hippo running at the same speed and a lion is chasing you. How do you get to safety?

Get off the merry-go-round.

Posted in Brain Teasers

Different Sizes, Colors and Shapes

What comes in different sizes, colors and shapes but creates a larger whole?

A jigsaw puzzle piece.

Posted in Riddles