Quandaries and Queries


for how many numbers less than 100 is the digit in the ones place half the digit in the tens place?


Hi Paul,

If xy is such a number then y is half of x, so x must be even. How many even digits are there? Once you know x how many choices are there for y?

Once you think you know how many there are, there are only a few, write them all down just to check.



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