Winning at Wimbledon

As a result of temporary magical powers, you have made it to the Wimbledon finals and are playing Roger Federer for all the marbles. However, your powers cannot last the whole match. What score do you want it to be when they disappear, to maximize your chances of hanging on for a win?

It sounds obvious that you should ask to be ahead two sets to love (it takes 3 out of 5 sets to win
the men’s), and in the third set, ahead 5-0 in games and 40-love in the sixth game. (Probably you
want to be serving, but if your serve is like mine, you might prefer Roger to be serving the sixth
game down 0-40 so that you can pray for a double fault.)

Not so fast! These solutions give you essentially 3 chances to get lucky and win, but you can
get six chances—with three services by you and three by Roger. You still want to be up two sets
to none, but let the game score be 6-6 in the third set and 6-0—in your favor, of course—in the
tiebreaker.

Credit goes to Peter Winkler for creating this.

Posted in Brain Teasers

Add Two To Eleven To Get One

When can you add two to eleven and get one as the correct answer?

When you add two hours to eleven o’clock to get one o’clock.

Posted in Riddles

Augustus’ Candy

Augustus loves candy and much to his delight, his three favorites are on sale. One each of gum, chocolate and caramel cost 40 cents. A caramel is over three times the price of gum. Six gums are worth more than chocolate. A caramel plus two gums cost less than chocolate. What is the price of each candy?

Gum = 4 cents
Chocolate = 23 cents
Caramel = 13 cents

Posted in Brain Teasers

Traveling Colorful Balls

Kevin, Charles, Larry and Alex are in a room that’s about 110 feet long. In front of them are 5 balls which are exactly 100 ft from the exit. The balls are yellow, purple, green, red and blue, respectively. Each man must carry a ball to the exit. After traveling 20 ft a ball will change color twice. The sequence of color changes is always the same: yellow, purple, green, red, and blue.

At 80 ft Kevin’s ball is red.
At 40 ft Larry’s ball is purple.
At 60 ft Charles’ ball is blue
At 100 ft Alex’s ball is purple.

What color ball was left behind?

The remaining ball was blue. Here’s a table of each ball and the color it changes to at 20, 40, 60, 80 and 100 ft. Kevin’s started out yellow, Larry’s was green, Charles’ was red and Alex began with a purple ball, leaving blue as the one nobody picked.

  20 ft 40 ft 60 ft 80 ft 100 ft
Yellow Green Blue Purple Red Yellow
Purple Red Yellow Green Blue Purple
Green Blue Purple Red Yellow Green
Red Yellow Green Blue Purple Red
Blue Purple Red Yellow Green Blue
Posted in Brain Teasers

How Many Legs?

You walk into a room and see a bed. On the bed there are two dogs, four cats, a giraffe, five cows and a duck. There are also three chickens flying above the bed. How many legs are on the floor?

Since all of the animals are on the bed and no other furniture is mentioned in the room, there are six legs on the floor. Four legs from the bed and your own two legs as you stand in the room, amazed that someone managed to get so many animals onto a bed. And the ceiling must be vaulted to fit a giraffe. Also, who’s on cleanup duty?

Posted in Brain Teasers

Twice Is 99 More Than Half

What number satisfies this requirement? Twice the number is 99 more than half of the number.

66.

2 × 66 = 132 and 132 – 66 / 2 = 99.

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

Plane Crash

A plane with 50 passengers crashes and everyone is killed, but there were only 49 bodies. How is this possible?

Two of the passengers were siamese twins.

Posted in Brain Teasers

I Prevent Escape

I prevent escape or intrusion,
Yet I also preserve and protect,

Thieves use me to get money,
From me they can often collect.

I’m the practice of a sport, but not on the lawn,
Your friends may get upset when I’m sat upon.

What am I?

Fence. Fences keep ne’er-do-wells out and protect people inside. A fence is a person who buys stolen goods to later resell them for a profit. Those who fence practice the sport of fencing. En garde! And people don’t like it when you sit on the fence in a heated debate. (Believe me, I speak from experience)

Posted in Riddles
Tagged with

What is the First Number of the Sequence?

If a number in a numeric sequence is 17 and the second number is 3, what is the first number?

I hesitated to add this because it’s poorly worded, ambiguous and the answer could be almost anything. I prefer teasers with a single answer, but there you go.

If you came up with a different answer and can explain how you did it, don’t think you’re wrong. It’s probably just as valid. Feel free to share yours in the comments.

My answer for the first number is 2.

Here’s how I got it.

The generic rule for a number in the sequence is: 2^(n – 1) + 1, where n is the position in the sequence.

Note: The teaser doesn’t specify the position of 17. In this case, it’s fifth.

Position 1: (so n = 1) is 2^(1 – 1) + 1 = 2

Position 2: 2^(2 – 1) + 1 = 3

Position 3: 2^(3 – 1) + 1 = 5

Position 4: 2^(4 – 1) + 1 = 9

Position 5: 2^(5 – 1) + 1 = 17

For the curious, the next 5 numbers of the sequence would be:

Position 6: 2^(6 – 1) + 1 = 33

Position 7: 2^(7 – 1) + 1 = 65

Position 8: 2^(8 – 1) + 1 = 129

Position 9: 2^(9 – 1) + 1 = 257

Position 10: 2^(10 – 1) + 1 = 513

Posted in Brain Teasers