How many 5 digit numbers exist that has 8 and 9 both appearing at least once? (For example: 12889)

Question

raden · Answer

881 ?

anonymous · Answer

There are a lot more

anonymous · Answer

Both have to be there 12349 is NOT OK

amoodarya · Answer

13122

anonymous · Answer

Nope

anonymous · Answer

That is wrong again, this problem is not so simple

amoodarya · Answer

digits of 2,3,4 can be 0 ,1,2,,,9
first digit cant be 0 so 1,2,..9 
last one 8,9

amoodarya · Answer

8 and 9 both appearing at least once 
at 2 digits or the last one ?

anonymous · Answer

First digit can be 1-9 every other digit can be 0-9. 
8and 9 has to be there somewhere, anywhere. 
LIke 98111 or 99998 or 18189 .....

amoodarya · Answer

ok i got the question now

anonymous · Answer

I found this question in a book for 13-14 year old students. 
I posted it here to check how hard it is. I believe this is too challenging for that age group

amoodarya · Answer

attachment

anonymous · Answer

That is it. Can I ask you what is your mathematical background?

amoodarya · Answer

you see my profile ?
i am going to be a professor in applied mathematics (branch of pde)

amoodarya · Answer

first time i do not understand the question !
but its for k11, k12 grade ! agree?

anonymous · Answer

Yeah I think so, I would not give this to a 14 year old, unless a very talented pupil. Havent looked at your profile

anonymous · Answer

I did applied maths at my final year. Love PDEs :D

amoodarya · Answer

branch of Partial differential equation

anonymous · Answer

I really lost it when I started doing some Laplace Tidal Equations, haha :)

amoodarya · Answer

it seems you are student of math ! yes ?

anonymous · Answer

I just finished my BsC

anonymous · Answer

Preparing for teaching now. 
Happy New Year and thanks for the help. I am off to party.

amoodarya · Answer

Happy New Year too and thanks show me 1 mistake (better understanding)