IMO 9^4-1 assuming we dont consider zero...4meonly wrote:How many integers from 1 to 10000, inclusive, do not conain digit 8?
I dont remember answers and OA.
what is the best approach to solve this question and this type of questions?
are u sure abt the Answer because for me its 9^4 = 6561.. when u consider zero.sudhir3127 wrote:4meonly wrote:I fond the answer
it is 6562
parallel_chase,
could you please explain?
one digit = 8 ways = 8
two digit = 8*9 ways = 72
three digit = 8*9*9 ways = 648
four digit = 8*9*9*9 ways = 729*8 = 5832
five digit = 1*1*1*1*1 ways = 1
8+72+648+5832+1 =6561
You are on the right way but I don't the logic
It means that for every place we have only 9 digits?Senator 153 wrote:It's just a way of checking; it's a computer script that counts the numbers that don't have eight in them.
I solved it using the same method as sudhir3127. 9 out of ten numbers will "survive" the test, per digit -- and four digits are tested, so it's 9^4.
Sudhir, can you pls. elaborate why you did 9^4?sudhir3127 wrote:are u sure abt the Answer because for me its 9^4 = 6561.. when u consider zero.sudhir3127 wrote:4meonly wrote:I fond the answer
it is 6562
parallel_chase,
could you please explain?
one digit = 8 ways = 8
two digit = 8*9 ways = 72
three digit = 8*9*9 ways = 648
four digit = 8*9*9*9 ways = 729*8 = 5832
five digit = 1*1*1*1*1 ways = 1
8+72+648+5832+1 =6561
You are on the right way but I don't the logic
Great. Thanks. That's an awesome explanation.parallel_chase wrote:Here is the process:
For example:
You have to find the number of integers between 1-999 that doesnt contain 3
formula : (9^3) - 1 = 728
Long method.
one digit number (1,2,4,5,6,7,8,9) = 8 ways
two digit number (0,1,2,4,5,6,7,8,9), first digit cannot be 0 = 8*9 ways
three digit number (0,1,2,4,5,6,7,8,9), first digit cannot be 0 = 8*9*9 ways
8 + 72 + 648 = 728
You have to find the number of integers between 1-1000 that doesnt contain 3
formula : 9^3 = 729
Long Method.
one digit number (1,2,4,5,6,7,8,9) = 8 ways
two digit number (0,1,2,4,5,6,7,8,9), first digit cannot be 0 = 8*9 ways
three digit number (0,1,2,4,5,6,7,8,9), first digit cannot be 0 = 8*9*9 ways
four digit number (0,1), first digit cannot be 0 and remaining digit cannot be greater than 0 = 1*1*1*1 = 1 ways
8 + 8*9 + 8*9*9 + 1 = 729
Try to solve the posted question with the same method.
"4meonly" i think you have got the wrong answer, the answer should 6561.
And the algorithm used by "Senator" is a computer program written probably in C++ or php, therefore i dont think he would be able to explain you the program unless you have any prior knowledge of computer programming.
Let me know if you still have any doubts.
