Kaitlyn’s Age Plus and Minus Three

Kaitlyn’s age plus three has an integer square root. Three years ago, Kaitlyn’s age was the square root.

How old is Kaitlyn?

Kaitlyn is 6 years old.

6 + 3 = 9, and 9 has an integer square root.

6 – 3 = 3, and 3 is the square root of 9.

Posted in Brain Teasers

Lies Behind Stars

It cannot be seen, it cannot be felt,
Cannot be heard, cannot be smelt,
Lies behind stars and under hills,
And empty holes it fills.
Comes first follows after,
Ends life kills laughter.

Darkness.

Posted in Riddles

Eight Eleven Five Sequence

Which two numbers are missing and where do they go in the sequence?

8, 11, 5, 14, 1, 7, 6, 10, 13, 3, 12, 2

The missing numbers are 4 and 9. The list is sorted alphabetically by the English spelling of the numbers, so four belongs after five and nine comes after fourteen.

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Eternally Joining In A Single Bite

With pointed fangs it sits in wait,
With piercing force it doles out fate,
Over bloodless victims proclaiming its might,
Eternally joining in a single bite

What is it?

A stapler.

Posted in Riddles

Largest Product

Using all the digits from 1 to 7, what two numbers have the largest product? For example, 1234 x 567 = 699678 but you can do much better than that.

742 x 6531 = 4,846,002.

A similar problem can be found in L.A. Graham’s Ingenious Mathematical Problems and Methods with a range of 1 to 9, but the principle remains the same – the numbers with the smallest difference produce the largest product. You start out with the highest two digits, 7 and 6, then attach 5 and 4, putting the smaller of the two digits with the larger number, giving you 74 and 65. The next two highest digits are 3 and 2, giving you 742 and 653. Finally, you add the 1 to the lower number. Page 80 has the details of that solution.

Posted in Brain Teasers

The Japanese IQ Test

Supposedly this is given as a test in Japan. I have no idea if that’s accurate.

There are 8 people who have to cross the river on a raft.

1. Policeman
2. Thief
3. Father
4. Boy 1
5. Boy 2
6. Mother
7. Girl 1
8. Girl 2

The rules are:

Only two people can cross at a time.
Only the adults can operate the raft.
The father can’t be with the girls unless the mother is there.
The mother can’t be with the boys unless the father is there.
The thief can’t remain with anyone unless the policeman is present.

How do you get them all across?

Instead of working it out by hand, here’s a flash version.

Click on the circle to start. Click on a person to put them on the raft and click on the lever to make the raft cross.

Here’s how I did it in 17 steps. Can you do it faster? Let me know in the comments.

1. Policeman (P)
2. Thief (T)
3. Father (F)
4. Boy 1 (B1)
5. Boy 2 (B2)
6. Mother (M)
7. Girl 1 (G1)
8. Girl 2 (G2)

1. P, T →
2. ← P

3. P, B1 →
4. ← P T

5. F, B2 →
6. ← F

7. F, M →
8. ← M

9. P, T →
10. ← F

11. M, F →
12. ← M

13. M, G1 →
14. ← P T

15. P, G2 →
16. ← P

17. P, T →

Posted in Brain Teasers

One Way I’m Feeling Normal

One way I’m feeling normal,
Another I’m extremely thin,
I could be a punishment,
Or the type who always wins.

I’m free from all impurity,
And you may have divined,
I have a keen edge,
But of course I am refined.

Fine.

The riddle refers to a variety of meanings of the word fine.

Feeling normal refers to when you feel fine.
Extremely thin refers to a fine thread.
A punishment refers to being charged a fee.
The one who wins refers to an athlete who is physically trained and hardened close to the limit of efficiency.
Free from impurity refers to measuring the fineness of precious metals.
A keen edge refers to a knife with a fine edge.
Refined refers to fine manners or elegance.

Posted in Riddles

A Leathery Snake

A leathery snake,
With a stinging bite,
I’ll stay coiled up,
Unless I must fight.

A whip.

Posted in Riddles

Nile Rebus

What does this represent?

          NILE
      HO   HO   HO

Nylon hose (literally nile on ho’s)

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Ten Men and Women

TEN = 20, 5, 14
MEN = 13, 5, 14

What do WOMEN equal using the same logic?

WOMEN = 23, 15, 13, 5, 14

The number is the letter’s position in the alphabet.

Posted in Brain Teasers