yvonne0923 wrote:
What fractional part of the total surface area of cube C is red?
(1) Each of 3 faces of C is exactly 1/2 red.
(2) Each of 3 faces of C is entirely white.
How to understand (1) Each of 3faces of C is exactly 1/2 red--->means 1/2 of 3 faces is red. and then where 1.5/6 = 1/4 come from?
How many faces does a cube have?
"6"
We need to consider both statements as true.
(1) Each of 3 faces of C is exactly 1/2 red.
Out of the 6 faces of a cube, 3 faces are exactly half red. We don't know anything about the other 3 faces of the cube. Thus, we wouldn't know what fractional part would be red.
Not Sufficient.
(2) Each of 3 faces of C is entirely white.
Out of the 6 faces of a cube, 3 faces are entirely white. We don't know anything about the other 3 faces of the cube. They could be all red or not red at all.
Not Sufficient.
Combining both and accepting both the statements as true:
3 faces are half red and the other 3 faces are entirely white. So, how much red for 6 faces?
3 are entirely white. Red=0 out of 3
3 faces are half red. Red=3/2 = 1.5 out of 3.
Fractional part which is red= 1.5/(3+3)=1.5/6=1/4=25%
Sufficient.
Ans: "C"
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