Question

combinations!

Answer 1

How many 4-digit positive integers are there, where each digit is positive, and no two adjacent digits are same?

Answer 2

can you help?? @Nnesha

Answer 3

Other than Trial and Error, I can't think of anyway @skylark06. Sorry

Answer 4

it's fine @Ahsome

Answer 5

yes @skylark06
what are the numbers?

Answer 6

like options?? @Haseeb96

Answer 7

yes option also
but what are those positive integers numbers .
because as u know the positive number are infinite

Answer 8

yeah actually it's combinations problem... no numbers are given. they are asking like what are possibilities. Like how many possibilities is there such that above condition is satisfied.

Answer 9

well options are
A. 1236
B. 3024
C. 4096
D. 4608
E. 6561 @Haseeb96 @ganeshie8

Answer 10

how many four digit numbers are there in total ?

Answer 11

there is mistake in the question or either u dont concentrate on the question
i am asking to u what are the positive numbers there given in the question ...

Answer 12

9000 i guess @ganeshie8

Answer 13

@Haseeb96 we need to find the total number of positive integers that have no common adjacent digits

Answer 14

yes so total four digit numbers = 9x10x10x10 = 9000

Answer 15

yep true )

Answer 16

lets subtract the numbers that have common adjacent digits from this

Answer 17

okay
would u tell me how can i do it ?
please explain @ganeshie8

Answer 18

how many ways the common adjacent digits can occur in a four digit number ?

Answer 19

hmmm yeah like 2 common digits adjacent to each other

Answer 20

wait a sec, this looks like donkey work
there must be a simpler way... lets think a bit

Answer 21

LOL donkey

Answer 22

lol simple way will be a lot better..
can't we count in hand the possibilities for each digit??

Answer 23

yeah im thinking the same

Answer 24

like, number of possibilities for each digit place
and multiply them together ?

Answer 25

yep!! right )

Answer 26

number of ways of choosing first digit = 9 :


because you cannot choose 0