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Geometry probability combo set

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by theachiever » Fri Dec 14, 2012 6:18 am
A large cube 10cm on a side is composed of smaller cubes 1 cm on a side. The large cube is printed red on its outside surfaces and then all the cubes are mixed in a drum. If one cube is selected randomly, which of the following is the approximate probability that the cube will have at least one red face?

A) 1:6

B) 1:5

C) 1:4

D) 1:3

E) 1:2
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by Anindya Madhudor » Fri Dec 14, 2012 7:25 am
Need to count the number of cubes with at least one red side.

Number of cubes with one side red = 10*10 + 9*10*2+ 10*8 + 8*8*2= 488

Probability = 488 /1000 = 1:2 (approx)
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