At a certain laboratory, chemical substances

[dddanny2006]

Source-Veritas prep

At a certain laboratory, chemical substances are identified by an unordered combination of 3 colors. If no chemical may be assigned the same colors, what is the maximum number of substances that can be identified using 7 colors?

The answer is 35-----------------7C3

However my doubt is that in the question its not given whether the colors can be repeated or not. They've said that no chemical may be assigned the same color,what this means is that the chemicals cant have same color.For example if Hydrochloric acid is identified by a Red,Green,Blue combination,then Sulphuric acid cant be represented by the same.

But the question doesnt make it clear whether Sulphuric acid can be represented by Green,Green,Green or Green,Red,Red.

Please help me with this one.

[RonPurewal]

I'd naturally read "three colors" as three different colors. (If the body of the coat is black, and each of the two sleeves is black, would you describe that coat as "three colors"? Probably not.)

But, sure, that should have been spelled out in the problem.