probability problem

MACHO-WIMP

The question is:
Two number cubes are rolled--one is red and the other is white. Find the probability that the red cube is a 6 and the sum of the two cubes is 10.

I said that it is 1/6 for being a 6 and since only a 4 can add up to 10 its 1/6*1/6=1/36. But my teacher said it was wrong. Please help!!!

HallsofIvy

I must say that I think you are correct and your teacher wrong. Are you sure you two are talking about the same problem? If the problem were just "one cube is 6 and the two sum to 10" then then you could get a 6 on either, and a four on the other: (1/6)(1/6)+ (1/6)(1/6)= 1/18.

Ray Vickson

You are correct; your teacher made a mistake. Your teacher would be correct IF you were not told the color of the "6" die---but you *were* told its color.

RGV