another probability question >_<?

Question

if the first digit of a seven-digit telephone number can never be a zero, what is the probability that your telephone number will have increasing digits (such as 234-5678).




please guys. i have a million of these for homework and i am getting the biggest head ache from them. i am doing so good in every subject but this one && it is frustrating. so in order to get the other 10 problems that I have on these could you tell me step-by-step on how you got the answer. i already tried it && ended up getting it wrong & becoming confused. so please solve this one for me so i can use this as an example.



thank youuuu

Answer 1

Post some of the others and I can help...but for this one...

You can use the numbers 0-9 in any position.

Digit 1 could be 0-9.
Digit 2 could be 0-9 and so on.

10 number possibilities for the first digit, 10 for the second, all the way to the 7th. So, there are 10^7 (10x10x10) different possible seven digit phone numbers.

OF those...you could have:

012-3456
123-4567
234-5678
345-6789

Only 4 increasing numbers!

Your probability is 4/10^7 or

1/2,500,000

Regards,

Mysstere

Answer 2

ok now clue if im right or not but here is my best answer
: you have 9 numbers to chose from you can only have 7 numbers so what about timesing 7 times 9 to get 63 or you have 9 of them startign with one, 9 of them starting with 2 ,9 of them starting with 3, because any higher you get less than seven #s unles syou count the # 10 in case you could have 567-8910 but that is if you count ten other wis its like (1x9)(2x9)(3x9)=4536 see if either one of these quesses are right