CPhill, in 3rd one, why have you repeated "10" , lets see it like this..

__ __ __ __

now we have 9 choices for the 1000th digit. (1,2,3,4,5,6,7,8,9)

next, after we have 5 choices for the ones place digit ( 0,2,4,6,8)

so now for the 100th place, we only have left 8 choices to choose from.

i thought that to made a no. divisible by 2 , only the last digit has to be even..? is that not true?

so that way we'll have 7 choices for the 10th position...

if we do it by 9*10*10*5

arent we repeating the digits?

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And CPhill in the 1st one arent you repeating the letters? what does "good word " mean?

this is getting really confusing, can you pls give me a more detailed answer?

Don't you know how to do the 2nd question?

thank you so much for your help!