Ok So i suck at probability.Help me out here.
A small business has its own internal phone system. Each phone number is four digits long The first digit must be 2 to indicate an internal call, and the second digit cannot be 0. How many internal phone numbers are possible for this company?
2007-09-24 09:34:00 · 8 answers · asked by Scented Marker 2 in Science & Mathematics ➔ Mathematics
Oh Wow.
I feel so stupid now.
Thanks guys.
=)
2007-09-24 09:46:31 · update #1
The first digit has to be a two: 1 possibility
The second digit cannot be a zero: 9 possibilities
Third and fourth digits can be anything: 10x10 possibilities.
Total = 1x9x10x10 = 900 possible numbers
2007-09-24 09:39:10 · answer #1 · answered by PMP 5 · 0⤊ 0⤋
There are four total digits.
For digit 1 you only have 1 option, 2
For digit 2 you have 9 options, 1-9
For digits 3 and 4 you have 10 options, 0-9
So, the number of possible combinations of numbers are:
1 * 9 * 10 * 10 = 900
That company is responsible for 900 different phone numbers.
2007-09-24 09:39:28 · answer #2 · answered by Jeremiah F 3 · 0⤊ 0⤋
900
If all digits were allowed in every place, there would be a maximum of 10*10*10*10, or 10,000 internal phone numbers.
With what you've stated, the first place is limited to a single digit - 2. And the second place is limited to one of 9 - all but 0. Given these restrictions, there is now a maximum of 1*9*10*10, or 900 phone numbers.
2007-09-24 09:43:15 · answer #3 · answered by skeptik 7 · 0⤊ 0⤋
Okay, so you have 4 digits to fill, but the first one has to be 2, so you have 6 to fill.
For the first position, you have 9 choices. For all the subsequent ones you have 10 choices, so 9(10)(10)or 9 x 10^2or 900
2007-09-24 09:39:49 · answer #4 · answered by ccw 4 · 0⤊ 0⤋
First digit: 2 OR only one possibility
Second digit: 1,2,3,4,5,6,7,8,9 OR only nine possibilities
Third digit: 0,1,2,3,4,5,6,7,8,9 OR ten possibilities
Fourth digit: 0,1,2,3,4,5,6,7,8,9 OR ten possibilities
Hence 1 X 9 X 10 X 10 = 900 total possible numbers
2007-09-24 09:40:58 · answer #5 · answered by tfeagin2003 2 · 0⤊ 0⤋
9 choices for second digit x 10 choices for third digit x 10 choices for fourth digit = 900
2007-09-24 09:39:53 · answer #6 · answered by fcas80 7 · 0⤊ 0⤋
first digit a 2. no 0 for second number.
The first possible number is 2100. The last possible number is 2999. subtract the two.
2999 - 2100 = 899 (+1 of the actual 2100)
900 possible phone numbers.
2007-09-24 09:42:15 · answer #7 · answered by Justin M 4 · 0⤊ 0⤋
The probability of drawing a black or a red is 1/2. The probability of drawing a specific suit is 1/4. a. Black (1/2) * red (1/2) = 1/4 b. Red (1/2) * spade (1/4) = 1/8 c. Heart (1/4) * heart (1/4) = 1/16
2016-05-17 21:14:11 · answer #8 · answered by ? 3 · 0⤊ 0⤋