Brain Teasers
1000 Prime Numbers
Determine the ones place value of the product of the first 1000 prime numbers. (What number would be in the ones position if you multiplied all of the first 1000 prime numbers together?)
Hint
All you need to know the first three prime numbers.Answer
ZERO. Any numbers multiplied by 2 and 5 (which are prime) result in a zero in the ones place.Hide Hint Show Hint Hide Answer Show Answer
What Next?
View a Similar Brain Teaser...
If you become a registered user you can vote on this brain teaser, keep track of which ones you have seen, and even make your own.
Solve a Puzzle
Comments
Good one! Had me really puzzled until I tried the first couple of products. Sneaky!
If I would have tryed to solve it yesterday, it would be much harder. Yesterday I knowticed that for avery n>5, n! will have '0' in ones position. I thought about that. 2*5=10 and any number multiplyed by 10 will have '0' in the end. And here is practicly the same case.
How could somebody who notices something like that not notice how they are spelling words?
Sorry I have no Math sense!
I am math stupid, so I didn't get it
eeeeeeeeeeeeeeeeezzzzzzzzzzzzzzzzzzzz
I did not get that!
that was ok
What???
i ain't good at math ..............................plus i thought it was boring
ps cat y don't u do that ur self ..........
ps cat y don't u do that ur self ..........
wont a 5 be in the one's place if you multiply 5 by an odd number?
That is only right if you have to multiply them all in order. Which is pretty much implied, but still.
This was like doing my taxes. I did not even feel like trying to solve this...it is more like a chore than a puzzle.
All that for nothing...literaly... zero?
But i'm sure the math buffs liked it.
All that for nothing...literaly... zero?
But i'm sure the math buffs liked it.
Bookmidget, the result is the same regardless if the order the numbers are multiplied.
Good teaser. For a couple seconds it seemed hard, but by the third second I had the answer.
Good teaser. For a couple seconds it seemed hard, but by the third second I had the answer.
To post a comment, please create an account and sign in.
Follow Braingle!