How to Save Gas

If you could chose to increase the average fuel economy of a car, which of these would save the most fuel?

1. 10mpg -> 12mpg
2. 12mpg -> 15mpg
3. 15mpg -> 20mpg
4. 20mpg -> 30mpg
5. 30mpg -> 60mpg

It turns out they all save the same amount of fuel.

If you travel 100 miles:

100 / 10 = 10 gallons used
100 / 12 = 8 1/3 gallons used

10 – 8 1/3 = 1 2/3 gallons saved

100 / 30 = 3 1/3 gallons used
100 / 60 = 1 2/3 gallons used

3 1/3 – 1 2/3 = 1 2/3 gallons saved

Posted in Brain Teasers

Falling Window Cleaner

A window cleaner is cleaning a window on the 25th floor of a skyscraper when he slips and falls. He has no safety equipment and nothing to soften his fall, yet he is not hurt. How can this be?

He was cleaning the inside of the window.

Posted in Brain Teasers

Keys to Unlock Your Soul

I am a box that holds keys without locks, yet they can unlock your soul. What am I?

A piano.

Posted in Riddles

Three Pills From the Doctor

Your doctor gives you three pills and tells you to take one every half hour. How much time will have passed by the time you’ve taken all three pills?

One hour. You take the first pill, then wait a half hour and take the second pill, then at the hour mark you take the third and last pill.

Posted in Brain Teasers

Characters In The Correct Order

Put the characters C D M L X in the correct order (not alphabetical).

X (10), L (50), C (100), D (500), M (1000). They’re Roman numerals in order from smallest to largest.

Posted in Brain Teasers

No New Digits

A six-digit number represented by ABCDEF (each letter represents a different number) can be multiplied by 2, 3, 4, 5, and 6 and yet no new digits appear in the result. As a matter of fact, all the digits are rotated. What is the number?

142857 (The first 6 digits of 1/7)

2 x 142857 = 285714
3 x 142857 = 428571
4 x 142857 = 571428
5 x 142857 = 714285
6 x 142857 = 857142

Posted in Brain Teasers

I Don’t Exist Unless You Cut Me

I don’t exist unless you cut me, but if you stab me I won’t bleed. I hate no one yet am abhorred by all. What am I?

A fart.

Posted in Riddles

Ancient Arabic

I’m Arabic, but if you speak English, you probably use me every day.

What am I?

The Arabic numerals, 1, 2, 3, etc.

Posted in Riddles
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Lending Money to Darlene

Franklin lent Darlene as much money as she already had, then she spent $10. The next day, Franklin lent her as much money as she now had and again, she spent $10. On the third day Franklin once again lent her as much money as she now had and she spent $10, leaving her broke. How much money did Darlene start with?

$8.75
You may have been tempted to guess $30 because $10 is spent three times, but that would mean she would have had $60 ($30 lent plus the $30 she already had), and $50 after spending $10. The rest of the numbers end up at higher than zero, so we know it has to be less than $30. Even starting at $10 leaves Darlene with $10 on the third day. Starting with $8.75 works out as follows.

Day 1: $8.75 (lent) + $8.75 (already had) – $10 (spent) = $7.50 (remaining)
Day 2: $7.50 + $7.50 – $10 = $5
Day 3: $5 + $5 – $10 = $0

Posted in Brain Teasers

A Voice With No Mouth

I am a voice without a mouth, throat or lungs. I know no language but speak in all tongues. What am I?

An echo.

Posted in Riddles