Suppose the tens digit of a whole number between 80 and 90 is greater than the ones digit,but less than twice the ones digit. If the integer is even, what is it's value?
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Ok so we know $80 < x <90$, so $x=8a$ where $a$ stands for some integer between 0 and 9. We know $a < 8$ because of the first condition.
We know have $a=1 , \dots ,7$, but the integer is even, meaning we get left with $a=2,4,6$. Using the last condition now, the tens digit must be strictly less than $2a$, meaning that $a=6$ is the only solution.
I believe the number you are looking for is $86$!
