What fractional part of the total surface area of cube C is

Yes. Each of 3 faces of C is exactly 1/2 red, so total of 3*1/2 = 1.5 faces out of 6 is red.

Target question: What fractional part of the total surface area of cube C is red

Statement 1: Each of 3 faces of C is exactly 1/2 red
Since we have no information about the other three faces, statement 1 is NOT SUFFICIENT
Consider these two counterexamples showing all six faces of the cube:

In the top example, the fraction of the total surface area that is red = (0.5 + 0.5 + 0.5 + 1)/6 = 2.5/6
In the bottom example, the fraction of the total surface area that is red = (0.5 + 0.5 + 0.5)/6 = 1.5/6
Since we can’t answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: Each of 3 faces of C is entirely white
Since we have no information about the other three faces, statement 2 is NOT SUFFICIENT
Consider these two counterexamples showing all six faces of the cube:

In the top example, the fraction of the total surface area that is red = (0.5 + 0.5 + 0.5)/6 = 1.5/6
In the bottom example, the fraction of the total surface area that is red = 0/6
Since we can’t answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
When we combine both statements, we know exactly what the six faces look like:

So, the fraction of the total surface area that is red = (0.5 + 0.5 + 0.5)/6 = 1.5/6
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer: C

Cheers,
Brent

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