common sense tells me that when I have two numbers x and y and I know one is a % of the other(in other words one is a fraction of the other) , then the answer is always x/y * 100 or y/x* 100 ......

Unfortunately, my common sense is fallible. Consequently, I'd rather rely on a more foolproof method, so that I don't misinterpret the question.

Let me follow your reasoning for a sec...you are not being consistent in the us of the word "is" and "of"

No offense, but I believe that by following the rules I'm actually the one being more consistent.

in case one: what % "of 10" "is 6"

you correctly did (% = z/100) * "of 10" = "is 6"

notice you implied "of 10" is the whole and "is 6" is the part

No, I implied that '

of' meant '

times' and '

is' meant '

='.

case 2: what % "is 6" "of 10"

you did (% = z/100) = "of 10" * "is 6" ...how does 6 of 10 translate to 6*10

'6 of 10' translates to '6 x 10' when '

of' means '

times'.

It basically comes down to how we interpret the usage of '

of' in this context. I'd never heard/seen this type of usage before, hence the query. I actually thought it was a trick question rather than a simple one.

Now, in no way am I advocating that the word '

of'

always means '

times'. If I had added the word '

out' to the question I would have interpreted it differently:

What percent is x out of y?In this case, I'm happy to concede that the question translates to

z/100 =

x/

y, because I recognise that '

out of' means '

divided by'. Take for example the following phrase:

'5

out of 10 people drink milk every day'.

We wouldn't say '5 of 10 people drink milk every day'. Having said that, I doubt a question would use the words '

out of' in the first place. The question would most likely just use '

/' symbol or express '

x/y' as a fraction using a graphic.

Either way, Ron admitted that this question was poorly worded, so I'm happy to leave it at that.