Math problem achiever

[americanpierg]

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How many four-digit numbers have only prime or odd digits in them? Assume all numbers are positive?

Some help here? I'm assuming either achiever is wrong, or the "prime or odd digits" means more than im understanding...


Also... what is the third term in the expansion of (x+3)^5... do we really need to know this.....

 

[UCB05]

How many four-digit numbers have only prime or odd digits in them? Assume all numbers are positive?

Some help here? I'm assuming either achiever is wrong, or the "prime or odd digits" means more than im understanding...

prime or odd number digits would be 1,2,3,5,7,9.
For the amount of four-digit numbers, wouldnt it then be 6^4?

 

[americanpierg]

prime or odd number digits would be 1,2,3,5,7,9.
For the amount of four-digit numbers, wouldnt it then be 6^4?

Yea...thats what I thought, they gave the answer as 4^4 = 256, seems like they just took prime numbers i think... dont know if it is a mistake or if there is a reason why in the wording.

 

[UCB05]

Also... what is the third term in the expansion of (x+3)^5... do we really need to know this.....

I highly doubt the actual DAT will ever give a problem like this. It's pretty complicated to figure it out unless you know the short formula for it. If you're curious,

http://en.wikipedia.org/wiki/Polynomial_expansion

 

[americanpierg]

I highly doubt the actual DAT will ever give a problem like this. It's pretty complicated to figure it out unless you know the short formula for it. If you're curious,

http://en.wikipedia.org/wiki/Polynomial_expansion

ahh thanks for the link. i saw the equation earlier and just totally decided not to learn it. saw that i can use pascal's triangle to solve it though. nice link

 

[sheetal27]

Prime Nos. are 1, 2, 3, 5, 7 and 2 is not an odd no. Thus it is 4^4.

I hope this helps.

 

[americanpierg]

Prime Nos. are 1, 2, 3, 5, 7 and 2 is not an odd no. Thus it is 4^4.

I hope this helps.

1 is not a prime number...