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

Five Pigeons on a Fence

Five pigeons are sitting on a fence. The farmer comes out and shoots one. How many are left?

None, the rest flew away at the sound of the gunshot. Or one (the dead pigeon).

Posted in Brain Teasers

A Blood Red Shroud

The thunder comes before the lightning,
And the lightning comes before the cloud,
The rain dries all the land it touches,
Wrapping the earth in a blood red shroud.

What am I?

A volcano.

Posted in Riddles

Yesterday and the Day After Tomorrow

When the day before yesterday was referred to as the day after tomorrow, the day that was then called yesterday was as far away from the day we now call tomorrow as yesterday is from the day which we shall now be able to speak of last Monday as a week ago yesterday. What day is it?

Thursday.

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

I’m Something You Might Eat But I Also Kill

I’m something you might eat, but I also kill.
I can cause blindness and burns.
Because of me, people lose limbs.
I’ve even been known to crash cars.

And yet I’m considered beautiful
Small children play with me and parents don’t mind.
Some people even live inside of me.

What am I?

Snow. Every kid has taken a bite of snow, but thousands of people die every year in snowstorms. Watch out for photokeratitis, otherwise known as snow blindness. And if you’re exposed to snow for too long, you can lose limbs to frostbite. Just an inch or two of snow makes them treacherous.

A recent snowfall makes the world white, and kids love to build snowmen, snow forts and have snowball fights. Some people live in igloos, built out of snow.

Posted in Riddles

What Boys Use, Girls Like and Parents Hate

Boys use it, girls like it, parents hate it. What is this 5-letter word?

The phone.

Posted in Riddles

A Metal Roof and a Glass Wall

I have a metal roof and a glass wall,
I burn and burn but never fall.

What am I?

A lantern.

Posted in Riddles
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Shoe Door Sticks Straight

Shoe, door, sticks, straight.

What word comes next?

Hen. The words are the last in each phrase from the children’s nursery rhyme.

One, two, buckle my shoe;
Three, four, Shut the door;
Five, six, Pick up sticks;
Seven, eight, Lay them straight:
Nine, ten, A big, fat hen;

Posted in Brain Teasers

Loud Noise When Changing Its Jacket

What makes a loud noise when changing its jacket, becomes larger but weighs less?

Popcorn.

Posted in Riddles