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

None There’ll Be

There is a word of letters three,
Add one letter to it and none there’ll be.

What is the word?

One. Add an ‘n’ to get none.

Posted in Riddles

Go Back!

Go back. You must strive to find a way to stay alive. What is 4+uo.5?

South. If you read the letters from back to front they make 5.ou+4, or south.

Posted in Brain Teasers

Three Digits in a Row

On a regular 12-hour digital clock how many times would the same three digits in a row be displayed (e.g. 1:11, 11:12, 12:22) in one day?

34 times. These 17 instances will be visible twice in a 24 hour period.

1:11
2:22
3:33
4:44
5:55
10:00
11:10
11:11
11:12
11:13
11:14
11:15
11:16
11:17
11:18
11:19
12:22

Posted in Brain Teasers

Never Ahead, Ever Behind

Never ahead, ever behind,
Yet flying swiftly past;
For a child I last forever,
For adults I’m gone too fast.

What am I?

Childhood.

Posted in Riddles
Tagged with

A Foot On Each Side

What has a foot on each side and one in the middle?

A yard stick.

Posted in Riddles

Jim’s Canoeing Adventure

Jim was canoeing on a lake when a sudden thunderstorm blew in tipped his boat. He swam to a rocky island about a mile from his family’s cottage and found a small, abandoned shack. Inside was an old kerosene lamp and a few matches. All the wood on the island was too damp to burn and the lamp was his only means of signaling for help but it only held an inch of kerosene, not enough to reach its short wick. How did he get the lamp burning to summon help?

Knowing kerosene and water wouldn’t mix and kerosene is less dense than water, he dipped the lamp in the lake and filled it with enough water so the kerosene rose to the top to cover the wick. The lamp was still burning an hour later when a motorboat rescued him.

Posted in Brain Teasers

Starts With T

What starts with a T, ends with a T, and has “T” in it?

A teapot.

Posted in Riddles

Brandon at the Carnival

Brandon was walking around at the carnival. A man called out from a booth and said, “If I can write your exact weight on this piece of paper, you have to pay me $50. If I can’t do it, I’ll pay you $50.”

Brandon checked the booth for a scale but saw nothing. He agreed. Since your weight can fluctuate by a pound or two, he decided that no matter what number the man wrote, he would just say he weighed a pound more or less. In the end, the man in the booth won the $50. How did he do it?

The man in the booth wrote the words, “Your exact weight” on the piece of paper. Brandon paid up.

Posted in Brain Teasers

Can’t Keep It Until You’ve Given It

You can’t keep this until you have given it.

A promise (or your word).

Posted in Riddles