Hello. Did you try anything? If you completed the other sums, you probably have at least one idea. Where did you get stuck?
Please take a few minutes to familiarize yourself with the forum's guidelines (AKA: Read Before Posting announcement); you may start with this summary. Thank you! :cool:
PS: Your duplicated thread has been deleted.
This is the only sum I am unable to solve in a problem set:
How many different 7-digit telephone numbers can be written if the digit 0 cannot appear among the first three digits? Remember that digits can be repeated.
I am in the tenth grade, studying Algebra II.
I think multiplying would work : 7 x 6 x 5 x 4 x 3 x 2 x 1, I’m not sure.
This is problem is part of a multi problem set, the other sums in the set are not related to each other.
Please help, in the form of a sample, way in which to solve this problem.
Thanks so much!
Mary, your solution will be: ?*?*?*?*?*?*? = answer
Will this be the write answer:
7x7x7x7x7x7x7=823,543.
Thanks a a lot for the help.
No, that is not the correct answer, but it is an answer correctly recognizing that arithmetic and thinking are more efficient than listing and counting when dealing with large numbers.Will this be the write answer:
7x7x7x7x7x7x7=823,543.
Thanks a a lot for the help.
There are \(\displaystyle 9^3\) ways to choose the first three digits.This is the only sum I am unable to solve in a problem set:
How many different 7-digit telephone numbers can be written if the digit 0 cannot appear among the first three digits? Remember that digits can be repeated.
I think I got it:
I need to muntiply 9x9x9x10x10x10x10= 7,290,000
Since in the first three numbers zero is not allowed so only (1,2,3,4,5,6,7,8,9) will be part of the first three sets. Thats nine numbers which will be 9x9x9
Next, since zero is allowed in the next four sets so I have these digits to work with (1,2,3,4,5,6,7,8,9,0,) that totals to 10, which makes its 10x10x10x10 for the next four sets.
Wonder what had happed to the grey matter in my head before, thanks a lot for the help !