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

Plane Crash Off Coast of Mexico

A plane crashed off the coast of Mexico and every single person died, yet there were two survivors. How could that happen?

There was a married couple.

Posted in Brain Teasers

An Alphabetical Rebus

What does this represent?

abcdefghijkmnopqrstuvwxyz

Noel (more literally no “l”).

I hope you have a great holiday season!

Posted in Brain Teasers
Tagged with

I Can Always Go Up, Never Down

I can always go up, never down,
I can always turn left, never right,
I am always hot when I’m cold

A ski lift.

Posted in Riddles

Copying Cassette Tapes

Joe and Andrea want to copy three 60-minute cassette tapes. They have a 2-cassette recorder to copy the tapes, allowing them to copy two tapes at a time. Each side takes 30 minutes to be copied, so two tapes can be copied in an hour and the third will take another hour. Andrea bets Joe she can copy all three tapes in 90 minutes. Does she win the bet?

In the first 30 minutes Andrea copies the A sides of tape 1 and 2.
In the second 30 minutes, she copies tape 1 side B and tape 3 side A (finishing Tape 1).
In the last 30 minutes, she copies tape 2 side B and tape 3 side B.

Posted in Brain Teasers

Ages Of Myself and My Brother

My current age, is the age of my 14 year-old brother plus one third of my age. How old will I be when my brother is twice his current age?

I will be 35. I am currently 21.

x = my current age

x = 14 + x/3
3x = 42 + x
2x = 42
x = 21 (so 14 years later, I'll be 35)
Posted in Brain Teasers

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

Fifty Quarters

You have fifty quarters on the table in front of you. You are blindfolded and cannot discern whether a coin is heads up or tails up by feeling it. You are told that x coins are heads up, where 0 < x < 50. You are asked to separate the coins into two piles in such a way that the number of heads up coins in both piles is the same at the end. You may flip any coin over as many times as you want.

How can you do it?

Take x coins, flip all of them and put them in one pile. The rest of the coins form the second pile.

Posted in Brain Teasers

How to Escape?

A man is trapped in a room with only two possible exits. Through the first door is a room with an enormous magnifying glass causing the blazing hot sun to instantly burn anything that enters. Through the second door there is a fire-breathing dragon. How does the man escape?

Leave through the first door at night when the sun is down.

Posted in Brain Teasers

Evianna’s New Love Interest

Evianna meets a man while attending her mother’s funeral. She becomes infatuated with him and he reciprocates the interest, but he leaves the funeral without giving her any contact information. She tries to locate him but is unsuccessful. Several days later she kills her sister.

Why did she do it?

Because she’s a psychopath. She killed her sister because she hoped the man would attend the funeral and she would get to see him again. This is one brain teaser that is probably best that you don’t get the correct answer. If you knew the answer right away and thought it was obvious, you may want to talk to someone.

Posted in Brain Teasers