Question

Tim wrote a seven -digit phone number on a piece of paper he later tore paper accidentally and the last two digits were lost.what is the maximum number of arrangements of two digits, using the digit 0 through 9, that he could use in attempting to reconstruct the correct phone number?

Answer 1

we wiil use the ncr or the npr and why

Answer 2

and how

Answer 3

So, there are 10 digits that could go in the first spot and there are 10 digits that could go in the second spot. 10 X 10 is equal to what?

Answer 4

what is the meaning of 0 through 9

Answer 5

Its basically saying how many combinations can you get with the numbers 0 through 9. Order does matter since this is a telephone number. With 0 as the lead coefficeint you can have:
0 0
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9

So you can have 10 combinations when 0 is the lead. Well you will get 10 more when 1 is the lead, 2 is the lead, 3 is the lead, 4 is the lead, 5 is the lead, 6 is the lead, 7 is the lead, 8 is the lead, and 9 is the lead. Add them all up and you get 100.

Answer 6

You get it?

Answer 7

i get your think but i want to know can i do it by calc using the npr or the ncr

Answer 8

too much work
there are 100 two digit numbers
use nothing but common sense

Answer 9

and if i do it by the npr its come 90 not 100

Answer 10

You don't need npr or ncr it's a logic question... very simple question at that.

Answer 11

You can also think of a 10x10 table (10 rows, 10 columns)

so there would be 10*10 = 100 entries. The entries would be this sequence

00,01,02,...,97,98,99

Answer 12

Yes exactly it's so simple that using something so complex will give you the wrong answer

Answer 13

Trust me I had this same question Last Year and made the same mistake you did.

Answer 14

but i need to know bec the my mr asking me i will use the ncr or the npr or none

Answer 15

i said to him none

Answer 16

Yes you won't use it because none is required

Answer 17

ok thnak u @shelbygt520

Answer 18

u are the best

Answer 19

npr and ncr are only used if repeated digits are NOT allowed

but in this case, a phone number like 555-0202 is possible. So repeated digits are allowed

Answer 20

and u too@jim_thompson5910

Answer 21

no problem

Answer 22

No probs.

Answer 23

ok bie friends

Answer 24

sorry but can i use the digit 10 @shelbygt520

Answer 25

or only 123456789

Answer 26

and 0

Answer 27

No because you are only aloud to use digits 0 through 9 or 0123456789

Answer 28

ok but if i aloud the 10 they wiil be 11*11

Answer 29

write or wrong

Answer 30

"10" is composed of "1" and "0"

shelbygt520 has the right idea

Answer 31

no because 10 would be 2 digits making it impossible to use it and another digit so you would essentially end up with 101

Answer 32

although as @jim_thompson5910 said 10 is composed of the digits 1 and 0 making it a combination within itself.

Answer 33

unto*

Answer 34

oh ya thanks friends

Answer 35

so the q can write as how many 2-digits formed from 0,1,2,3,4,5,6,7,8,9 @shelbygt520

Answer 36

write or wrong

Answer 37

@jim_thompson5910

Answer 38

what i writ wrong or write

Answer 39

yeah how many ways to make a 2 digit number

Answer 40

can i write it like this so the q can write as how many 2-digits formed from 0,1,2,3,4,5,6,7,8,9 write or wrong

Answer 41

@jim_thompson5910

Answer 42

yeah that's one way to think of it

how many ways to form a 2 digit number

Answer 43

the other digits of the phone number don't matter

Answer 44

thank u @jim_thompson5910

Answer 45

sure thing