The answer is that product y is greater than product x by 853%.

Assume:
A1: $828.74


A2: $87.00
A3: =(A1/A2-1), formatted as %

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Your answer gets to exactly what I do not understand--

By what logic or rule or understanding do you know which # to divide by which #?

Mark

The answer to that is found in the way you posed your original question:
Therefore, 'y' is the numerator and 'x' is the denominator.

In this case, with x=$87.00 and y=$828.74:
'x' is 10.5% of 'y' ($87.00/$828.74)*100, which makes it 89.5% less than 'y' ($87.00/$828.74 -1)*100; and
'y' is 953% of 'x' ($828.74/$87.00)*100, which makes it 853% more than 'x' ($828.74/$87.00 -1)*100.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]