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Question

any quick fix?

thearch · Answer

numbers XX5 are always odd and there is 1 XX5 every 10
so (1000-100)*1/10=90

numbers X5X can be even or odd.
We have 10 of them every 100.
Of these 10, 5 are even and X55 has been already counted.
we have 900*4/100=36

numbers 5XX can be even or odd.
we have 100 of them.
Of these 100, 50 are even and 50 odd.
Of the 50 odd, 10 5X5 have been already counted.
Of the 50 odd, 4 55X have been already counted.
total is 36.

Total with 5 as a digit is 90+36+36=162
Answer is 450-162=288

Hope this helps even if it is wrong.

MA · Answer

total no of integers from 100 to 1000=(1000-100)+1=901
no of odd integers from 100 to 1000=(901-1)/2=450
total= 162
the required number=450-162=288

Dan · Answer

total # = 901
even # = 451

so odd # = 450

100 to 200: 14 5's
so 14 * 8 = 112 (not counting the 500's)

500's: 100 numbers; out of which half is odd with 5 = 50 numbers.

total = 112 + 50 = 162

odd and no 5's = 450 - 162= 288. Sooooo Easy!!! :-D