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

Paula and Quincy

Paula had four times the money that Quincy had, but after Paula gave Quincy $33, Quincy had 3 times as much as Paula.

How much did they each start with?

Paula had $48 and Quincy had $12.

If Q is the amount Quincy had, then 3(4Q – 33) = Q + 33

Solved, Q = 12.

Posted in Brain Teasers

Useless Keys

What keys don’t unlock any doors?

Piano keys, keyboard keys, monkey, donkey, turkey, jockey, hockey, doohickey, malarkey and passkey. There may be others, but you get the drift.

Posted in Brain Teasers

Which Are True and Which Are False?

A. When a car is driven forwards the wheels rotate counter-clockwise.
B. If a clock is put forward 1 1/4 hours the minute hand moves through 450°
C. When a clock reads 4.10 the acute angle between the hands is exactly 60°

A. False – The near-side wheels rotate counter-clockwise, but the far-side wheels rotate clockwise.
B. True
C. False – The acute angle is a little more than 60° because by the time the minute hand reaches 10, the hour hand will have moved slightly past the 4.

Posted in Brain Teasers

The Truck and the Plane

A delivery truck from the post office is sent to the airport to meet a cargo plane at its planned arrival time. The plane lands ahead of schedule and its contents are brought toward the post office by bicycle. After a half hour, the bicycle meets the truck and the mail is transferred.

The truck returns from the post office 20 minutes early. How early did the plane arrive? (Assume all transactions are instantaneous)

The delivery truck arrived back 20 minutes early, so it would have taken 20 minutes to go from where it met the bicycle to get to the airport and back. Therefore, the bicycle and truck met when the truck was 10 minutes from the airport. Adding those 10 minutes to the 30 minutes the truck had already driven to meet the bicycle means the plane arrived 40 minutes ahead of schedule.

Posted in Brain Teasers

More You Take Away, The Bigger I Get

The more you take from me, the bigger I get. What am I?

A hole.

This is quite similar to It Cannot Be Seen and Weighs Nothing.

Posted in Riddles

Only Self-Enumerating Number

What is the only self-enumerating number in English?

Four. The number four has four letters, making it self-enumerating. Interestingly, there are no self-enumerating numbers in French.

Posted in Brain Teasers

To Frighten a Thief

What four letters frighten a thief?

OICU (Oh I see you!)

Posted in Riddles

The Tortoise, Onion and Tomato

What is three-eighths tortoise, two-fifths onion and two-sixths tomato?

Toronto

3/8 tortoise = TOR (the first three letters)
2/5 onion = ON (the first two letters)
2/6 tomato = TO (the first two letters)

Posted in Riddles
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A Problem In Many People’s Lives

I am a problem in many people’s lives. At times (even more than once) I’m useful. The older I grow, the less useful I become. Who am I?

Credit or debt. Debt is a problem in many people’s lives, but in order to go to school or make a large purchase, it can be useful. As your debt grows older, it’s more unpleasant than useful.

Posted in Riddles