Question

Combinations and permutations
I must find what is the total number of 7 digit registration numbers, when the digits available are 0, 1, 2, 3, 4, 5, 6, 7, 9, the registration numbers are issued in ascending order and you cannot have 6 and 9 in the same line,

Answer 1

As shown in the above question, the total number of boat registration numbers staring with 1 is 9360.

Answer 2

I am confused. Free cupcake for right answer.

Answer 3

it cannot start wid 0, right ?

Answer 4

yes

Answer 5

looks yummy :)

Answer 6

ty :) ok so you have worked our # of permutations starting wid 1 = 9360.
we will start from there

Answer 7

*worked out

Answer 8

k

Answer 9

# permutations starting wid 1 : 9360
# permutations starting wid 2 : 9360
# permutations starting wid 3 : 9360
# permutations starting wid 4 : 9360
# permutations starting wid 5 : 9360
# permutations starting wid 7 : 9360

Answer 10

thats trivial to figure out, lets see how many start wid 6, and how many start wid 9

Answer 11

If the string starts wid 6, we have to exclude 9. that leaves us wid 7 digits to fill in remaining 6 empty spaces : 7p6 = 7!/(7-6)!

Answer 12

similarly, If the string starts wid 9, we have to exclude 6. that leaves us wid 7 digits to fill in 6 empty spaces : 7p6 = 7!/(7-6)!

Answer 13

Add them all to get the total 7 digit permutations w/o 6 and 9 in same line :-
6x9360 + 2x 7p6

Answer 14

is this right?

Answer 15

which q ? 6th one ?

Answer 16

yes

Answer 17

looks wrong, you didnt add 2x7p6

Answer 18

is this correct?

Answer 19

oops ! ive overlooked ur previous pdf. your previous pdf is right
66240 = \(\checkmark\)

Answer 20

cool. can u look at my latest question