Geometry probability combo set

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 116
Joined: Wed Oct 03, 2012 10:44 pm
Thanked: 5 times
Followed by:1 members

Geometry probability combo set

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
Resilience is a trait that manifests in an individual when he/she faces consistent failures motivating them to succeed in the end.
Source: — Problem Solving |

Senior | Next Rank: 100 Posts
Posts: 85
Joined: Mon Nov 12, 2012 11:12 am
Thanked: 8 times
Followed by:2 members

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)